Find excluded files no vcs (#590)

* Add a new test for the case where no vcs is detected

It can happens with unsupported VCS or no VCS at all (building from an
archive).
I copy the test_complete test and run it in a temporary directory where no VCS
should be detected.
I also modified the complete directory fixture directory, I can create a new
one if it's better

* Fix find_excluded_files to works without vcs

Fix #585