tests: Do GC after each test

This makes it easier to understand which test causes
ResourceWarnings.

Author: 1st1

uvloop/_testbase.py

@@ -73,6 +73,11 @@ def setUp(self):
     def tearDown(self):
         self.loop.close()
 
+        # GC to show any resource warnings as the test completes
+        gc.collect()
+        gc.collect()
+        gc.collect()
+
         if getattr(self.loop, '_debug_cc', False):
             gc.collect()
             gc.collect()