Improving error message in test_instfreqplot

ltfatpy/tests/gabor/test_instfreqplot.py

@@ -107,7 +107,8 @@ class TestInstfreqplot(unittest.TestCase):
         for inputs, outputs in data:
             out = instfreqplot(**inputs)
             msg = ('Wrong value in output of instfreqplot with inputs ' +
-                   str(inputs))
+                   str(inputs) +
+                   '\nMaximal error: ' + str(np.max(np.abs(outputs[0] - out))))
             assert_allclose(out, outputs[0], atol=1e-13, err_msg=msg)