Remove workaround for decimal module

The decimal module is available on all Python versions supported by
psycopg2. It has been available since Python 2.4. No need to catch an
ImportError.

https://docs.python.org/2/library/decimal.html

lib/__init__.py

@@ -72,14 +72,10 @@ _ext.register_adapter(type(None), _ext.NoneAdapter)
 # Register the Decimal adapter here instead of in the C layer.
 # This way a new class is registered for each sub-interpreter.
 # See ticket #52
-try:
-    from decimal import Decimal
-except ImportError:
-    pass
-else:
-    from psycopg2._psycopg import Decimal as Adapter
-    _ext.register_adapter(Decimal, Adapter)
-    del Decimal, Adapter
+from decimal import Decimal
+from psycopg2._psycopg import Decimal as Adapter
+_ext.register_adapter(Decimal, Adapter)
+del Decimal, Adapter
 
 
 def connect(dsn=None, connection_factory=None, cursor_factory=None, **kwargs):

tests/test_cursor.py

@@ -98,11 +98,7 @@ class CursorTests(ConnectingTestCase):
             cur.mogrify(u"SELECT %s;", (snowman,)))
 
     def test_mogrify_decimal_explodes(self):
-        # issue #7: explodes on windows with python 2.5 and psycopg 2.2.2
-        try:
-            from decimal import Decimal
-        except:
-            return
+        from decimal import Decimal
 
         conn = self.conn
         cur = conn.cursor()
@@ -138,12 +134,8 @@ class CursorTests(ConnectingTestCase):
         self.assertEqual(42, curs.cast(20, '42'))
         self.assertAlmostEqual(3.14, curs.cast(700, '3.14'))
 
-        try:
-            from decimal import Decimal
-        except ImportError:
-            self.assertAlmostEqual(123.45, curs.cast(1700, '123.45'))
-        else:
-            self.assertEqual(Decimal('123.45'), curs.cast(1700, '123.45'))
+        from decimal import Decimal
+        self.assertEqual(Decimal('123.45'), curs.cast(1700, '123.45'))
 
         from datetime import date
         self.assertEqual(date(2011, 1, 2), curs.cast(1082, '2011-01-02'))