Handle deprecation of inspect.getargspec

getargspec has been deprecated in py3 with plans to remove it in py3.6.
The recommendation is to move to inspect.signature, but the results
of that call are different than the existing one.

There is also getfullargspec available under py3 that was originally
deprecated, but for the sake of handling 2/3 code, it has been
un-deprecated. This call uses signature internally, but returns a mostly
compatible result with what getargspec did. This handles getargspec
deprecation by just using getfullargspec instead if it is available.

Change-Id: I32dd29bde99f9d59c2b0e14dd6782162963b43ae

oslo_db/sqlalchemy/enginefacade.py

@@ -13,7 +13,6 @@
 
 import contextlib
 import functools
-import inspect
 import operator
 import threading
 import warnings
@@ -27,6 +26,7 @@ from oslo_db import exception
 from oslo_db import options
 from oslo_db.sqlalchemy import engines
 from oslo_db.sqlalchemy import orm
+from oslo_db.sqlalchemy import utils
 
 
 class _symbol(object):
@@ -970,7 +970,7 @@ class _TransactionContextManager(object):
 
     def __call__(self, fn):
         """Decorate a function."""
-        argspec = inspect.getargspec(fn)
+        argspec = utils.getargspec(fn)
         if argspec.args[0] == 'self' or argspec.args[0] == 'cls':
             context_index = 1
         else:

oslo_db/sqlalchemy/utils.py

@@ -18,6 +18,7 @@
 
 import collections
 import contextlib
+import inspect as pyinspect
 import itertools
 import logging
 import re
@@ -1227,6 +1228,25 @@ def suspend_fk_constraints_for_col_alter(
                 )
 
 
+def getargspec(fn):
+    """Inspects a function for its argspec.
+
+    This is to handle a difference between py2/3. The Python 2.x getargspec
+    call is deprecated in Python 3.x, with the suggestion to use the signature
+    call instead.
+
+    To keep compatibility with the results, while avoiding deprecation
+    warnings, this instead will use the getfullargspec instead.
+
+    :param fn: The function to inspect.
+    :returns: The argspec for the function.
+    """
+    if hasattr(pyinspect, 'getfullargspec'):
+        return pyinspect.getfullargspec(fn)
+
+    return pyinspect.getargspec(fn)
+
+
 class NonCommittingConnectable(object):
     """A ``Connectable`` substitute which rolls all operations back.