There is a fragile test case that attempts to match error messages from PCRE library

[qbtf]

When I was in the process of making this library compile under macOS, I noticed that a specific test case kept failing. It is this case for CLI covering queries containing invalid regex. It should emit an error, and my test program did emit one, but the case still failed.

Upon further investigation, it emitted error messages that does not contain the words defined in the harness. I consider this case fragile -- it should not assume that the PCRE library emit specific error massage, because it can vary across implementations and the library itself can change wording deliberately. I suggest that the test case matches FilterKey: Error compiling regular expression as it is defined in librdb itself.