test: Issue#40 unittest to check for specific repo files

[bertuss]

Fixes #40

Checklist

• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the [Contribution Guide] and my PR follows them.
• I updated my branch with the master branch.
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation about the functionality in the appropriate .md file
• I have added in line documentation to the code I modified

Short description of what this PR does:

Adds unit test to check that the list of required files exist in this repository.

[mbernier]

It seems there's an error when this test is run:

======================================================================
ERROR: test_repository_files_exists (__main__.TestRepository)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test/__init__.py", line 107, in test_repository_files_exists
    msg=self.file_not_found_message.format('" or "'.join(file_path)))
ValueError: zero length field name in format

Can you please give this a look?

[bertuss]

Sorry about that, was expecting Travis to error out, so I didn't double check all the errors.
Python 2.6 required an index when using format. Working as expected now.

[SendGridDX]

All committers have signed the CLA.

[mbernier]

Thanks for making that change!!

[thinkingserious]

Hello @bertuss,

Thanks again for the PR!

We appreciate your contribution and look forward to continued collaboration. Thanks!

Team SendGrid DX