Testlib: Standardize debug messages in testlib

[castulo]

When there are failures in the creation of test resources, it is very difficult to determine the cause, the use of debug messages make it easier, however debug messages are very inconsistent right now, some functions have many, some functions don't have debug messages at all. We should come up with a standardized way of showing these in functions so it makes debugging of tests easier.

[otaviobp]

debug_msg also doesn't work when \n is added to the message.