PEP-8 fixes

Signed-off-by: Michal Čihař <michal@cihar.com>
Fix typo

Signed-off-by: Michal Čihař <michal@cihar.com>
Proper validation of repository link

We need to skip most of the validation if link is invalid (we can not
validate file matches and most of other parameters).

Fixes #532.

Signed-off-by: Michal Čihař <michal@cihar.com>