Handle deprecation of inspect.getargspec

The getargspec function is deprecated in python3 and in some cases the
deprecation warning can actually cause unit test failures[1]. Follow
Sean's example[2] to smartly use the right inspect function and avoid
deprecation warnings.

[1] http://logs.openstack.org/47/524747/3/check/openstack-tox-py35/1585cb9/testr_results.html.gz
[2] https://review.openstack.org/#/c/521979/

Change-Id: Ia0ac9a79f9faf618aeafae4621afaf1db62ed1e5

keystone/common/manager.py

@@ -26,6 +26,11 @@ from keystone.i18n import _
 
 LOG = log.getLogger(__name__)
 
+if hasattr(inspect, 'getfullargspec'):
+    getargspec = inspect.getfullargspec
+else:
+    getargspec = inspect.getargspec
+
 
 def response_truncated(f):
     """Truncate the list returned by the wrapped function.
@@ -85,7 +90,7 @@ class _TraceMeta(type):
 
     @staticmethod
     def wrapper(__f, __classname):
-        __argspec = inspect.getargspec(__f)
+        __argspec = getargspec(__f)
         __fn_info = '%(module)s.%(classname)s.%(funcname)s' % {
             'module': inspect.getmodule(__f).__name__,
             'classname': __classname,