Manage setup_vcs problems better

[humitos]

I introduced a bug at e0c84056e

If the repo is invalid (.setup_vcs fails), we catch the exception, log it and continue as if everything went correct.

https://github.com/rtfd/readthedocs.org/blob/19e709089d645ac712a4c16b06a6083dbacd0539/readthedocs/projects/tasks.py#L612-L636

[stsewd]

I guess it was merged before it was finished?

#4804 (comment)

[humitos]

I think you are right. I'd revert this PR for now and propose a better solution for this.

[stsewd]

I guess we can remove the try except block only from self.sync_repo(). The another block was already catching a general exception.