Fixed problems with proc package

[Kaszanas]

Unit testing yielded couple of errors during the processing of the video.
All of them were connected to the use of proc package.

• If this is a bugfix, I have provided code that clearly demonstrates the problem and that works when used with this PR
• I have added a test to the test suite, if necessary
• I have properly documented new or changed features in the documention, or the docstrings
• I have properly documented unusual changes to the code in the comments around it
• I have made note of any breaking/backwards incompatible changes

[tburrows13]

Sorry, I didn't mean to get rid of the 'draft' status.

[Kaszanas]

@tburrows13 not a problem I haven't marked it as ready for review because I already fixed the problem and I do not have the exact code that is required to get the same result when it comes to reproducing the errors that were involved.

I am not sure when I will be able to recreate those. If the changes are acceptable "as is" then I think that it is reasonable to merge.

Otherwise if any more code is needed to prove that it is a fix. It will have to wait.

There were exactly 3 errors while processing video files.
I will try to post the resulting errors here ASAP.

[Julian-O]

I am confused by the purpose of the check before terminating:

if self.proc.poll() is not None:
    self.proc.terminate()

Firstly, is there any harm in skipping the check and just calling terminate every time?

Secondly, the return code definition says:

 A None value indicates that the process hasn’t terminated yet.

So, this seems to call terminate only if it has already been terminated.

I am not an expert at subprocess, so this could just be my confusion rather than a bug.

[coveralls]

Coverage decreased (-0.02%) to 67.317% when pulling d8e1aea on Kaszanas:master into b2ed1f6 on Zulko:master.

[tburrows13]

Adding .wait() was added as part of another PR some time ago so is no longer shown here in the 'Files changed'. Checking .poll() has come up again in #1296.

[mondeja]

Since @Kaszanas has not posted the errors, #1296 has been merged and the source code has changed a lot since this pull, I'm closing this. Feel free to reopen it if your errors persist.