Program exit successfully if path doesn't contain any test

[jlausuch]

When the path given by the parameter --test or -t exists but it doesn't contain any .py, the program exits with success message:

mkdir /tmp/somedir
qatrfm -t /tmp/somedir --tfvar image=$image     
INFO     qatrfm.cli  : All tests passed

It should actually exit with "No test files found" or similar with exit code !=0

[jlausuch]

I also noticed, that if you give a directory which contains any .py file, it will try to execute it. So we should really make sure that the Class we load and execute has inheritance from TrfmTestCase

[asmorodskyi]

execution of qatrfm --test s
will produce following output :

 File "/usr/bin/qatrfm", line 10, in <module>
    sys.exit(cli())
  File "/usr/lib/python3.6/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python3.6/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3.6/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3.6/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/home/asmorodskyi/source/team/qatrfm-lib/qatrfm/cli.py", line 153, in cli
    testcases = find_testcases(Path(test))
  File "/home/asmorodskyi/source/team/qatrfm-lib/qatrfm/cli.py", line 90, in find_testcases
    return load_testcases(basedir, files)
  File "/home/asmorodskyi/source/team/qatrfm-lib/qatrfm/cli.py", line 67, in load_testcases
    tf_file = find_corresponding_tf_file(i)
  File "/home/asmorodskyi/source/team/qatrfm-lib/qatrfm/cli.py", line 40, in find_corresponding_tf_file
    assert(f.is_file())
AssertionError

the problem here that with --test param we somehow getting into failure related to tf file