Report how much memory is leaking in vbo memory test

tests/test_vbo_memusage.py

@@ -1,45 +1,54 @@
 import pygamegltest
 import os
+
 # We have to import at least *one* VBO implementation...
 from OpenGL import GL, arrays
 from OpenGL.arrays import vbo
+
 try:
     import psutil
 except ImportError:
     psutil = None
 try:
-    unicode 
+    unicode
 except NameError:
-    unicode = str 
+    unicode = str
     long = int
 import pytest
 import gc
+
 try:
     import numpy as np
 except ImportError:
     np = None
 
+
 def get_current_memory():
     return psutil.Process(os.getpid()).memory_info().rss
 
-@pytest.mark.skipif(not psutil,reason='No psutil available')
-@pytest.mark.skipif(not np,reason='No Numpy available')
+
+@pytest.mark.skipif(not psutil, reason="No psutil available")
+@pytest.mark.skipif(not np, reason="No Numpy available")
 @pygamegltest.pygametest()
 def test_sf_2980896():
     """Test SF#2980896 report of memory leak on VBO transfer"""
     data = arrays.GLfloatArray.zeros((1000,))
     memory = get_current_memory()
-    for i in range(100): 
+    for i in range(100):
         new_vbo = vbo.VBO(data)
         with new_vbo:
             # data is transferred to the VBO
             assert new_vbo is not None, new_vbo
         new_vbo.delete()
-        del new_vbo 
+        del new_vbo
         gc.collect()
         GL.glFinish()
-        if i  < 1: 
+        if i < 1:
             # the *first* call can load lots of libraries, etc...
             memory = get_current_memory()
         else:
-            assert get_current_memory() - memory < 200, """Shouldn't have any (or at least much) extra RAM allocated..."""
+            current = get_current_memory()
+            assert current - memory < 200, (
+                """Shouldn't have any (or at least much) extra RAM allocated, lost: %s"""
+                % (current - memory)
+            )  # fails only when run in the whole suite...