Made compatible with python 2.7 and tried to fix weird bug I didn't encounter at own system

tests/keras_contrib/callbacks/dead_relu_detector_test.py

@@ -26,15 +26,17 @@ def check_print(do_train, expected_warnings, nr_dead=None, perc_dead=None):
     stdoutput = out.getvalue()  # get prints, can be something like: "Layer dense (#0) has 2 dead neurons (20.00%)!"
     str_to_count = "dead neurons"
     count = stdoutput.count(str_to_count)
-    
+
     sys.stdout = saved_stdout   # restore stdout
-    
+
     assert expected_warnings == count
     if expected_warnings and (nr_dead is not None):
-        assert 'has {} dead'.format(nr_dead) in stdoutput
+        str_to_check = 'has {} dead'.format(nr_dead)
+        assert str_to_check in stdoutput, '"{}" not in "{}"!'.format(str_to_check, stdoutput)
     if expected_warnings and (perc_dead is not None):
-        assert 'neurons ({:.2%})'.format(perc_dead) in stdoutput
-        
+        str_to_check = 'neurons ({:.2%})'.format(perc_dead)
+        assert str_to_check in stdoutput, '"{}" not in "{}"!'.format(str_to_check, stdoutput)
+
 
 def test_DeadDeadReluDetector():
     n_samples = 9
@@ -173,4 +175,5 @@ def test_DeadDeadReluDetector_conv():
 
 
 if __name__ == '__main__':
-    pytest.main([__file__])
+    # pytest.main([__file__])
+    test_DeadDeadReluDetector_conv()