diff --git a/.travis.yml b/.travis.yml
index 897bb736..d83f3d92 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -23,10 +23,10 @@ script:
 - |
   if [ "$TEST_TYPE" = lint ]; then
     echo "Checking Python code lint."
-    flake8
+    flake8 graphene
     exit
   elif [ "$TEST_TYPE" = build ]; then
-    py.test --cov=graphene
+    py.test --cov=graphene graphene examples
   fi
 after_success:
 - |
diff --git a/graphene/generators/__init__.py b/graphene/generators/__init__.py
index 1f46ebc6..497dddde 100644
--- a/graphene/generators/__init__.py
+++ b/graphene/generators/__init__.py
@@ -1,4 +1,10 @@
-from .definitions import GrapheneInterfaceType, GrapheneObjectType, GrapheneScalarType, GrapheneEnumType, GrapheneInputObjectType
+from .definitions import (
+    GrapheneInterfaceType,
+    GrapheneObjectType,
+    GrapheneScalarType,
+    GrapheneEnumType,
+    GrapheneInputObjectType
+)
 from .utils import values_from_enum
 
 
diff --git a/graphene/generators/definitions.py b/graphene/generators/definitions.py
index 70eba044..68251acb 100644
--- a/graphene/generators/definitions.py
+++ b/graphene/generators/definitions.py
@@ -1,4 +1,6 @@
-from graphql import GraphQLObjectType, GraphQLInterfaceType, GraphQLScalarType, GraphQLEnumType, GraphQLInputObjectType
+from graphql import (GraphQLEnumType, GraphQLInputObjectType,
+                     GraphQLInterfaceType, GraphQLObjectType,
+                     GraphQLScalarType)
 
 
 class GrapheneGraphQLType(object):
@@ -6,6 +8,7 @@ class GrapheneGraphQLType(object):
     A class for extending the base GraphQLType with the related
     graphene_type
     '''
+
     def __init__(self, *args, **kwargs):
         self.graphene_type = kwargs.pop('graphene_type')
         super(GrapheneGraphQLType, self).__init__(*args, **kwargs)
diff --git a/graphene/generators/utils.py b/graphene/generators/utils.py
index 43fc79e5..96eb9016 100644
--- a/graphene/generators/utils.py
+++ b/graphene/generators/utils.py
@@ -1,4 +1,5 @@
 from collections import OrderedDict
+
 from graphql.type import GraphQLEnumValue
 
 
diff --git a/graphene/relay/connection.py b/graphene/relay/connection.py
index 802ee5f0..d29e9b2a 100644
--- a/graphene/relay/connection.py
+++ b/graphene/relay/connection.py
@@ -1,7 +1,7 @@
-import re
 import copy
+import re
+from collections import Iterable
 from functools import partial
-from collections import Iterable, OrderedDict
 
 import six
 
@@ -35,8 +35,8 @@ class ConnectionMeta(ObjectTypeMeta):
             interfaces=[],
         )
 
-        Edge = attrs.pop('Edge', None)
-        edge_fields = props(Edge) if Edge else {}
+        edge_class = attrs.pop('Edge', None)
+        edge_fields = props(edge_class) if edge_class else {}
         edge_fields = get_fields(ObjectType, edge_fields, ())
 
         connection_fields = copy_fields(Field, get_fields(ObjectType, attrs, bases))
@@ -108,7 +108,8 @@ class IterableConnectionField(Field):
         iterable = resolver(root, args, context, info)
         # if isinstance(resolved, self.type.graphene)
         assert isinstance(
-            iterable, Iterable), 'Resolved value from the connection field have to be iterable. Received "{}"'.format(iterable)
+            iterable, Iterable), 'Resolved value from the connection field have to be iterable. Received "{}"'.format(
+            iterable)
         connection = connection_from_list(
             iterable,
             args,
diff --git a/graphene/relay/mutation.py b/graphene/relay/mutation.py
index 60b84c17..f619a658 100644
--- a/graphene/relay/mutation.py
+++ b/graphene/relay/mutation.py
@@ -31,11 +31,11 @@ class ClientIDMutationMeta(MutationMeta):
             description=None,
         )
 
-        Input = attrs.pop('Input', None)
+        input_class = attrs.pop('Input', None)
 
         cls = super_new(cls, name, bases, dict(attrs, _meta=options))
 
-        input_fields = props(Input) if Input else {}
+        input_fields = props(input_class) if input_class else {}
         input_local_fields = copy_fields(InputField, get_fields(InputObjectType, input_fields, ()))
         output_fields = copy_fields(Field, get_fields(ObjectType, attrs, bases))
 
diff --git a/graphene/relay/node.py b/graphene/relay/node.py
index 99121232..fbccfd4b 100644
--- a/graphene/relay/node.py
+++ b/graphene/relay/node.py
@@ -6,11 +6,10 @@ from graphql_relay import from_global_id, node_definitions, to_global_id
 
 from ..types.field import Field
 from ..types.interface import Interface
-from ..types.objecttype import ObjectType, ObjectTypeMeta, is_objecttype
+from ..types.objecttype import ObjectType, ObjectTypeMeta
 from ..types.options import Options
-from .connection import Connection
-
 from ..utils.copy_fields import copy_fields
+from .connection import Connection
 
 
 # We inherit from ObjectTypeMeta as we want to allow
@@ -40,7 +39,8 @@ class NodeMeta(ObjectTypeMeta):
         cls = type.__new__(cls, name, bases, dict(attrs, _meta=options))
         get_node_from_global_id = getattr(cls, 'get_node_from_global_id', None)
         id_resolver = getattr(cls, 'id_resolver', None)
-        assert get_node_from_global_id, '{}.get_node_from_global_id method is required by the Node interface.'.format(cls.__name__)
+        assert get_node_from_global_id, '{}.get_node_from_global_id method is required by the Node interface.'.format(
+            cls.__name__)
         node_interface, node_field = node_definitions(
             get_node_from_global_id,
             id_resolver=id_resolver,
diff --git a/graphene/types/__init__.py b/graphene/types/__init__.py
index d226b3e5..e43ad73a 100644
--- a/graphene/types/__init__.py
+++ b/graphene/types/__init__.py
@@ -1,5 +1,4 @@
-from .objecttype import ObjectType
-from .interface import Interface
+from .objecttype import ObjectType, Interface
 from .scalars import Scalar, String, ID, Int, Float, Boolean
 from .schema import Schema
 from .structures import List, NonNull
diff --git a/graphene/types/argument.py b/graphene/types/argument.py
index ad4b20a4..fa816a5f 100644
--- a/graphene/types/argument.py
+++ b/graphene/types/argument.py
@@ -41,7 +41,7 @@ class Argument(GraphQLArgument, OrderedType):
 
     @classmethod
     def copy_from(cls, argument):
-        if isinstance (argument, (GraphQLArgumentDefinition, Argument)):
+        if isinstance(argument, (GraphQLArgumentDefinition, Argument)):
             name = argument.name
         else:
             name = None
diff --git a/graphene/types/datetime.py b/graphene/types/datetime.py
index d2dd27bf..bdf5870e 100644
--- a/graphene/types/datetime.py
+++ b/graphene/types/datetime.py
@@ -1,20 +1,27 @@
 from __future__ import absolute_import
 
 import datetime
-try:
-    import iso8601
-except:
-    raise ImportError("iso8601 package is required for DateTime Scalar.\nYou can install it using: pip install iso8601.")
+
 from graphql.language import ast
 
 from .scalars import Scalar
 
+try:
+    import iso8601
+except:
+    raise ImportError(
+        "iso8601 package is required for DateTime Scalar.\n"
+        "You can install it using: pip install iso8601."
+    )
+
 
 class DateTime(Scalar):
 
     @staticmethod
     def serialize(dt):
-        assert isinstance(dt, (datetime.datetime, datetime.date)), 'Received not compatible datetime "{}"'.format(repr(dt))
+        assert isinstance(dt, (datetime.datetime, datetime.date)), (
+            'Received not compatible datetime "{}"'.format(repr(dt))
+        )
         return dt.isoformat()
 
     @staticmethod
diff --git a/graphene/types/enum.py b/graphene/types/enum.py
index c1d382ba..0f8ba122 100644
--- a/graphene/types/enum.py
+++ b/graphene/types/enum.py
@@ -2,6 +2,7 @@ from collections import OrderedDict
 
 import six
 
+from ..generators import generate_enum
 from ..utils.is_base_type import is_base_type
 from .options import Options
 from .unmountedtype import UnmountedType
@@ -11,8 +12,6 @@ try:
 except ImportError:
     from ..utils.enum import Enum as PyEnum
 
-from ..generators import generate_enum
-
 
 class EnumTypeMeta(type):
 
@@ -43,10 +42,10 @@ class EnumTypeMeta(type):
 
         return cls
 
-    def __prepare__(name, bases, **kwargs):
+    def __prepare__(name, bases, **kwargs):  # noqa: N805
         return OrderedDict()
 
-    def __call__(cls, *args, **kwargs):
+    def __call__(cls, *args, **kwargs):  # noqa: N805
         if cls is Enum:
             description = kwargs.pop('description', None)
             return cls.from_enum(PyEnum(*args, **kwargs), description=description)
@@ -57,5 +56,5 @@ class Enum(six.with_metaclass(EnumTypeMeta, UnmountedType)):
 
     @classmethod
     def from_enum(cls, enum, description=None):
-        Meta = type('Meta', (object,), {'enum': enum, 'description': description})
-        return type(Meta.enum.__name__, (Enum,), {'Meta': Meta})
+        meta_class = type('Meta', (object,), {'enum': enum, 'description': description})
+        return type(meta_class.enum.__name__, (Enum,), {'Meta': meta_class})
diff --git a/graphene/types/field.py b/graphene/types/field.py
index f5316896..2f687381 100644
--- a/graphene/types/field.py
+++ b/graphene/types/field.py
@@ -1,7 +1,8 @@
-from collections import OrderedDict
 import inspect
+from collections import OrderedDict
 
-from graphql.type import GraphQLField, GraphQLInputObjectField, GraphQLFieldDefinition
+from graphql.type import (GraphQLField, GraphQLFieldDefinition,
+                          GraphQLInputObjectField)
 from graphql.utils.assert_valid_name import assert_valid_name
 
 from ..utils.orderedtype import OrderedType
diff --git a/graphene/types/inputobjecttype.py b/graphene/types/inputobjecttype.py
index 40549994..46a1ffdd 100644
--- a/graphene/types/inputobjecttype.py
+++ b/graphene/types/inputobjecttype.py
@@ -1,5 +1,6 @@
 import six
 
+from ..generators import generate_inputobjecttype
 from ..utils.copy_fields import copy_fields
 from ..utils.get_fields import get_fields
 from ..utils.is_base_type import is_base_type
@@ -9,9 +10,6 @@ from .options import Options
 from .unmountedtype import UnmountedType
 
 
-from ..generators import generate_inputobjecttype
-
-
 class InputObjectTypeMeta(type):
 
     def __new__(cls, name, bases, attrs):
diff --git a/graphene/types/interface.py b/graphene/types/interface.py
index fac33216..56fc0ebb 100644
--- a/graphene/types/interface.py
+++ b/graphene/types/interface.py
@@ -1 +1,3 @@
 from .objecttype import Interface
+
+__all__ = ['Interface']
diff --git a/graphene/types/json.py b/graphene/types/json.py
index 42393957..f4bc632b 100644
--- a/graphene/types/json.py
+++ b/graphene/types/json.py
@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 
 import json
+
 from graphql.language import ast
 
 from .scalars import Scalar
diff --git a/graphene/types/mutation.py b/graphene/types/mutation.py
index 6874ae3d..018f8ef9 100644
--- a/graphene/types/mutation.py
+++ b/graphene/types/mutation.py
@@ -16,10 +16,10 @@ class MutationMeta(ObjectTypeMeta):
         if not is_base_type(bases, MutationMeta):
             return type.__new__(cls, name, bases, attrs)
 
-        Input = attrs.pop('Input', None)
+        input_class = attrs.pop('Input', None)
 
         cls = cls._create_objecttype(cls, name, bases, attrs)
-        field_args = props(Input) if Input else {}
+        field_args = props(input_class) if input_class else {}
         resolver = getattr(cls, 'mutate', None)
         assert resolver, 'All mutations must define a mutate method in it'
         cls.Field = partial(Field, cls, args=field_args, resolver=resolver)
diff --git a/graphene/types/objecttype.py b/graphene/types/objecttype.py
index cb073e8e..c2825b70 100644
--- a/graphene/types/objecttype.py
+++ b/graphene/types/objecttype.py
@@ -46,10 +46,10 @@ class ObjectTypeMeta(type):
 
         return cls._create_objecttype(cls, name, bases, attrs)
 
-    def get_interfaces(cls, bases):
+    def get_interfaces(cls, bases):  # noqa: N805
         return (b for b in bases if issubclass(b, Interface))
 
-    def is_object_type(cls):
+    def is_object_type(cls):  # noqa: N805
         return issubclass(cls, ObjectType)
 
     @staticmethod
diff --git a/graphene/types/scalars.py b/graphene/types/scalars.py
index 9d82654a..d6966e19 100644
--- a/graphene/types/scalars.py
+++ b/graphene/types/scalars.py
@@ -3,12 +3,11 @@ import six
 from graphql import (GraphQLBoolean, GraphQLFloat, GraphQLID, GraphQLInt,
                      GraphQLString)
 
+from ..generators import generate_scalar
 from ..utils.is_base_type import is_base_type
 from .options import Options
 from .unmountedtype import UnmountedType
 
-from ..generators import generate_scalar
-
 
 class ScalarTypeMeta(type):
 
@@ -44,8 +43,8 @@ def construct_scalar_class(graphql_type):
     # class String(Scalar):
     #     class Meta:
     #         graphql_type = graphql_type
-    Meta = type('Meta', (object,), {'graphql_type': graphql_type})
-    return type(graphql_type.name, (Scalar, ), {'Meta': Meta})
+    meta_class = type('Meta', (object,), {'graphql_type': graphql_type})
+    return type(graphql_type.name, (Scalar, ), {'Meta': meta_class})
 
 
 String = construct_scalar_class(GraphQLString)
diff --git a/graphene/types/tests/test_scalars.py b/graphene/types/tests/test_scalars.py
index c79b6910..8a2b7b12 100644
--- a/graphene/types/tests/test_scalars.py
+++ b/graphene/types/tests/test_scalars.py
@@ -4,9 +4,9 @@ import pytest
 
 from graphene.utils.get_graphql_type import get_graphql_type
 from graphql import graphql
-from graphql.type import (GraphQLBoolean, GraphQLFloat, GraphQLInt,
-                          GraphQLScalarType, GraphQLString, GraphQLFieldDefinition)
 from graphql.language import ast
+from graphql.type import (GraphQLBoolean, GraphQLFieldDefinition, GraphQLFloat,
+                          GraphQLInt, GraphQLScalarType, GraphQLString)
 
 from ..field import Field
 from ..objecttype import ObjectType
diff --git a/graphene/utils/is_graphene_type.py b/graphene/utils/is_graphene_type.py
index 384f1b6c..013d9d2d 100644
--- a/graphene/utils/is_graphene_type.py
+++ b/graphene/utils/is_graphene_type.py
@@ -8,8 +8,6 @@ def is_graphene_type(_type):
     from ..types.interface import Interface
     from ..types.scalars import Scalar
     from ..types.enum import Enum
-    from ..relay.mutation import ClientIDMutation
-    from ..relay.connection import Connection
 
     return inspect.isclass(_type) and hasattr(_type, '_meta') and issubclass(_type, (
         Interface,
diff --git a/setup.cfg b/setup.cfg
index 89077559..a6669b9e 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,5 +1,5 @@
 [flake8]
-exclude = setup.py,docs/*,*/examples/*
+exclude = setup.py,docs/*,*/examples/*,graphene/utils/enum.py,tests
 max-line-length = 120
 
 [coverage:run]