Use ReadFile.splitlines() rather than readlines

A few places in the code open a file "manually" rather than using our
wrapper function, because they need an array with the lines. Combining
the result of utils.ReadFile with splitlines() we get rid of the
exceptions.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>