Make inflection package truly optional

Fix #9291

docs/api-guide/schemas.md

@@ -56,10 +56,11 @@ The following sections explain more.
 
 ### Install dependencies
 
-    pip install pyyaml uritemplate
+    pip install pyyaml uritemplate inflection
 
 * `pyyaml` is used to generate schema into YAML-based OpenAPI format.
 * `uritemplate` is used internally to get parameters in path.
+* `inflection` is used to pluralize operations more appropriately in the list endpoints.
 
 ### Generating a static schema with the `generateschema` management command
 

rest_framework/compat.py

@@ -46,6 +46,15 @@ try:
 except ImportError:
     yaml = None
 
+# inflection is optional
+try:
+    from inflection import pluralize
+except ImportError:
+    def pluralize(text):
+        if not text.endswith('s'):
+            text += "s"
+        return text
+
 
 # requests is optional
 try:

rest_framework/schemas/openapi.py

@@ -14,7 +14,7 @@ from django.utils.encoding import force_str
 from rest_framework import (
     RemovedInDRF315Warning, exceptions, renderers, serializers
 )
-from rest_framework.compat import uritemplate
+from rest_framework.compat import pluralize, uritemplate
 from rest_framework.fields import _UnvalidatedField, empty
 from rest_framework.settings import api_settings
 
@@ -247,8 +247,6 @@ class AutoSchema(ViewInspector):
                 name = name[:-len(action)]
 
         if action == 'list':
-            from inflection import pluralize
-
             name = pluralize(name)
 
         return name