Fix tox failed on PyPy

runtests.py

@@ -4,20 +4,22 @@ try:
 except ImportError:
     import unittest
 
-import atexit
-import gc
-gc.set_debug(gc.DEBUG_UNCOLLECTABLE)
+import sys
+if not hasattr(sys, 'pypy_version_info'):
+    import atexit
+    import gc
+    gc.set_debug(gc.DEBUG_UNCOLLECTABLE)
 
-@atexit.register
-def report_uncollectable():
-    print('uncollectable objects')
-    for obj in gc.garbage:
-        print(obj)
-        if hasattr(obj, '__dict__'):
-            print(obj.__dict__)
-        for ref in gc.get_referrers(obj):
-            print("referrer:", ref)
-        print('---')
+    @atexit.register
+    def report_uncollectable():
+        print('uncollectable objects')
+        for obj in gc.garbage:
+            print(obj)
+            if hasattr(obj, '__dict__'):
+                print(obj.__dict__)
+            for ref in gc.get_referrers(obj):
+                print("referrer:", ref)
+            print('---')
 
 import pymysql.tests
 unittest.main(pymysql.tests)