Suppress the warning message about "Couldn't import the

ExtensionClass-based base class ..." from Persistence/__init__.py.  It's
bad to see that when running tests.

This was fixed quite a while ago in ZODB 3.3, but the code appeared to
get lost in the latest round of merges.  By eyeball, I didn't detect any
other lossage in test.py.

test.py

@@ -655,6 +655,8 @@ def main(module_filter, test_filter, libdir):
 
 def process_args(argv=None):
     import getopt
+    import warnings
+
     global module_filter
     global test_filter
     global VERBOSE
@@ -676,6 +678,20 @@ def process_args(argv=None):
     global functional
     global test_dir
 
+    # Persistence/__init__.py generates a long warning message about the
+    # the failure of
+    #     from _Persistence import Persistent
+    # for the benefit of people expecting that to work from previous (pre 3.3)
+    # ZODB3 releases.  We don't need to see that msg every time we run the
+    # test suite, though, and it's positively unhelpful to see it in this
+    # context.
+    # NOTE:  "(?s)" enables re.SINGLELINE, so that the ".*" can suck up
+    #        newlines.
+    warnings.filterwarnings("ignore",
+        message="(?s)Couldn't import the ExtensionClass-based base class.*"
+                "There are two possibilities:",
+        category=UserWarning)
+
     if argv is None:
         argv = sys.argv