Fix repo hook error upon upload

Some lines of the presubmit message are coming back as
bytes instead of a string using pyton3. So, ensure
each line is a str before checking contents.

Also, send code 77 back to ensure that the error message
is actually printed

Test: repo upload
Change-Id: Ieecd6228318b3001098ac45e4767b8bf46826387
1 file changed