Added code to raise exception with string

[stef405]

I added two lines to VideoClip.py that raises an exception if a user passes in a string as the color parameter. This is in reaction to this Bug. The problem the original user faced was that it raised a ValueError. The user inputted 'black' as the color in ColorClip, which is not an acceptable parameter for the function. Instead, I just created some code that checks if color is a string, and raises an exception that mentions the wrong user input. In the future, a user should hopefully realize quicker that they passed in incorrect input with the Exception message, instead of not knowing why a ValueError was thrown later on.

To test_color() in test_VideoClip.py, I added a test that attempts to create a Clip with color = 'black'. The test passes, since an exception should be thrown when color is passed in as a string.

I also checked for PEP8 conventions in both files, and none of the code I added resulted in a style complaint.

• I have provided code that clearly demonstrates the bug and that only works correctly when applying this fix
• I have added suitable tests demonstrating a fixed bug or new/changed feature to the test suite in tests/
• I have properly documented new or changed features in the documentation or in the docstrings
• I have properly explained unusual or unexpected code in the comments around it

[keikoro]

@stef405 I fixed the code for the checkboxes and moved it to the end of your PR description. They are meant to be ticked off to give an idea of what was done at a quick glance.

[keikoro]

Looks like the formatting needs some more work.

[coveralls]

Coverage: 83.917% (-0.8%) from 84.751% when pulling fe13e43 on stef405:master into 86fd511 on Zulko:master.

[coveralls]

Coverage: 84.048% (-0.7%) from 84.751% when pulling fe13e43 on stef405:master into 86fd511 on Zulko:master.

[coveralls]

Coverage: 84.048% (-0.7%) from 84.751% when pulling fe13e43 on stef405:master into 86fd511 on Zulko:master.

[coveralls]

Coverage: 84.513% (-0.2%) from 84.751% when pulling fe13e43 on stef405:master into 86fd511 on Zulko:master.

[coveralls]

Coverage: 84.828% (+0.08%) from 84.751% when pulling 3aa1a4d on stef405:master into 86fd511 on Zulko:master.

[coveralls]

Coverage: 84.73% (-0.02%) from 84.751% when pulling fe13e43 on stef405:master into 86fd511 on Zulko:master.

[coveralls]

Coverage: 84.73% (-0.02%) from 84.751% when pulling fe13e43 on stef405:master into 86fd511 on Zulko:master.

[keikoro]

@stef405 You can combine the changes into one commit and force-push the PR, no need to add to the log when it's something so small which could have been caught earlier.

[stef405]

@keikoro I combined the commits. There should now be only one commit associated with this PR