fix : minor bug in matplotlib version fixed

test/warning_test.py

@@ -17,7 +17,7 @@ True
 True
 >>> with open('data.json', 'w') as fp:
 ...     json.dump({'data1': [0], 'data2': [0], 'matplotlib_version': '0'}, fp)
->>> with warns(RuntimeWarning, match="Source matplotlib version(0) is different from yours, plots may be different."):
+>>> with warns(RuntimeWarning, match=r"Source matplotlib version(.*) is different from yours, plots may be different."):
 ...     g = GenerativeImage(lambda x,y: 0, lambda x,y: 0, data=open('data.json', 'r'))
 >>> os.remove('data.json')
 """