Display of error empty: fmbt3-editor tries to search contents of byte String, but should search decoded string instead

[BLuedtke]

Hello everyone,
I'm using the fmbt3-editor for creating python aal models. This issue concerns the devel branch (havent tested master), particularly utils3/fmbt3-editor. I am using Ubuntu 20.04 LTS.

When the model/code I invoke in fmbt3-editor throws an error, the view switches to the error tab. This is expected. There it says "Complete unformatted error output:". However, the error output after that is empty. In the console with which I started fmbt3-editor, I can see the error message being printed though. Interestingly, it is printed as a byte string, with the "b"-prefix.

In method _doGenerateTest of fmbt3-editor, the contents of this error (byte-) string are analyzed. This happens before showError is called, and here in _doGenerateTest, the _test_errormsg has to be set to the error message that should be displayed by showError.
In this method on line 1231 (of fmbt3-editor), it is checked whether some specific strings are contained in the error output (output[1] to be precise). Based on my tests, this check fails, and the method returns directly. However, if I change line 1231 to this:
if fmbt_exitstatus == 0 or "pass:" in output[1].decode('utf-8') or "inconc:" in output[1].decode('utf-8') or "fail:" in output[1].decode('utf-8'):
and change line 1239 to
self._test_errormsg = output[1].decode('utf-8')
then it works. Maybe one would also add a check for whether output[1] is None or Empty, to avoid exceptions here.

It seems like the "string in other string" search does not work if the string to search is a bytestring and not decoded. Now, I am not sure if this will be the same for every operating system. It could also depend on the version of python I suppose. There could also be other valid reasons for not decoding the string, which I haven't discovered yet.
As the fix is relatively easy, I'm fine with just modyfying the fmbt3-editor file on my machine, but fixing this in the repo would be more convenient. I'm kinda busy atm but if my stress cools down a bit, I could also submit a pull request.