Comment 4 for bug 1506215

testr just accept one reg-exp argument it is not sufficient for the whole logic! (It should have dedicated accept_re + reject_re)

In case if we have defined black_list + regexp specified, the still simple and not too bad thing what we can do now is to have testr list-tests (with one regexp arg) for getting the test case list, and then filtering that list even more based on the blacklist file content.

We need to convert a list of test cases (exact test names) to a regexp.

So the the `normal flow` will be:
 1. testr list-tests
 2. filter the listed tests based on the extra regexps from the black_list
 3. convert the list to regexp

PS.: I also noticed the current code would call testr too many times in case of the print_skips would be used.