Support tuples of ast.ExceptHandler names

In Python 2, it's legal to receive and unpack a tuple as an exception
value:

    except (socket.herror, socket.gaierror) as (errno, errstring):

This is in fact the documented exception value of some socket functions:

 - https://docs.python.org/2/library/socket.html#socket.herror
 - https://docs.python.org/2/library/socket.html#socket.gaierror

Fixes #98

src/pep8ext_naming.py

@@ -454,8 +454,7 @@ def _extract_names(assignment_target):
     target_type = type(assignment_target)
     if target_type is ast.Name:
         yield assignment_target.id
-        return
-    if target_type in (ast.Tuple, ast.List):
+    elif target_type in (ast.Tuple, ast.List):
         for element in assignment_target.elts:
             element_type = type(element)
             if element_type is ast.Name:
@@ -466,13 +465,16 @@ def _extract_names(assignment_target):
             elif not PY2 and element_type is ast.Starred:  # PEP 3132
                 for n in _extract_names(element.value):
                     yield n
-        return
-    if target_type is ast.ExceptHandler:
+    elif target_type is ast.ExceptHandler:
         if PY2:
-            yield assignment_target.name.id
+            # Python 2 supports unpacking tuple exception values.
+            if isinstance(assignment_target.name, ast.Tuple):
+                for name in assignment_target.name.elts:
+                    yield name.id
+            else:
+                yield assignment_target.name.id
         else:
             yield assignment_target.name
-        return
 
 
 def is_mixed_case(name):

testsuite/N806_py2.py

@@ -0,0 +1,13 @@
+# python_version < '3'
+#: Okay
+def f():
+    try:
+        f()
+    except (A, B) as (a, b):
+        pass
+#: N806
+def f():
+    try:
+        f()
+    except (A, B) as (good, BAD):
+        pass