Add deprecation warnings to all deprecated APIs

A large change throughout the library has ensured that all objects, parameters,
and behaviors which have been noted as deprecated or legacy now emit
``DeprecationWarning`` warnings when invoked.   As the Python 3 interpreter now
defaults to displaying deprecation warnings, as well as that modern test suites
based on tools like tox and pytest tend to display deprecation warnings,
this change should make it easier to note what API features are obsolete.

See the notes added to the changelog and migration notes for further
details.

Fixes: #4393
Change-Id: If0ea11a1fc24f9a8029352eeadfc49a7a54c0a1b

1 files changed, 11 insertions, 5 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/psycopg2.py b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
index 98e703fb5..8a15a8559 100644
--- a/lib/sqlalchemy/dialects/postgresql/psycopg2.py
+++ b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
@@ -407,11 +407,17 @@ class _PGNumeric(sqltypes.Numeric):
 
 class _PGEnum(ENUM):
     def result_processor(self, dialect, coltype):
-        if util.py2k and self.convert_unicode is True:
-            # we can't easily use PG's extensions here because
-            # the OID is on the fly, and we need to give it a python
-            # function anyway - not really worth it.
-            self.convert_unicode = "force_nocheck"
+        if util.py2k and self._expect_unicode is True:
+            # for py2k, if the enum type needs unicode data (which is set up as
+            # part of the Enum() constructor based on values passed as py2k
+            # unicode objects) we have to use our own converters since
+            # psycopg2's don't work, a rare exception to the "modern DBAPIs
+            # support unicode everywhere" theme of deprecating
+            # convert_unicode=True. Use the special "force_nocheck" directive
+            # which forces unicode conversion to happen on the Python side
+            # without an isinstance() check.   in py3k psycopg2 does the right
+            # thing automatically.
+            self._expect_unicode = "force_nocheck"
         return super(_PGEnum, self).result_processor(dialect, coltype)