bears/general: Add FileModeBear

Closes https://github.com/coala/coala-bears/issues/2370

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Current codecov failure at 99.91% can be ignored - https://travis-ci.org/coala/coala-bears/jobs/561920971 shows the new bear is getting 100% test coverage

It should be possible to get executable bit working correctly on Windows, and this PR cant close the issue without executable support, as executable support is the primary motivation for this bear, and the need to include Windows was a consistent message throughout the comments of the issue.

@jayvdb The bear works fine for Windows (as it only reads the file permissions and doesn't change them), the problem was I couldn't test it properly on Windows since Python can only set read-only flags on it. One way to test this could be to rename the file to the extension .exe which automatically sets the executable flag.

@bkhanale ,

... the problem was I couldn't test it properly on Windows

If you can not test it, you have no way to determine that is works, and you should not attempt to argue that it does work.

I can see a mile away it does not achieve what the issue requested.

No you do not get to create a useless test by renaming files to .exe . That isnt what the issue asked for.

And even ignoring the fact the bear doesnt work, the test method test_x_to_x_permissions on Windows does:

os.chmod(FILE_PATH, stat.S_IXUSR)
os.chmod(FILE_PATH, stat.S_IRUSR)

That is not a test of the bear, it it. That is wrong. Fix it.

https://github.com/coala/coala-bears/pull/2912/files#r294035442 asked you two months ago to document why you were doing that. You havent done that. Why not?

Why are you using custom test logic instead of verify_local_bear? Is there something about this bear which means verify_local_bear doesnt work for any of the tests? If so, why not use self.check_invalidity?

And even ignoring the fact the bear doesnt work, the test method test_x_to_x_permissions on Windows does:

I guess that he did to roll back changes made to the file permissions (which I guess defaults to read permission).

Why are you using custom test logic instead of verify_local_bear? Is there something about this bear which means verify_local_bear doesnt work for any of the tests? If so, why not use self.check_invalidity?

Yep, you can use check_validity wherever you're not checking for the message statements.