sibylbot: incorrect error message for certain plugin loads

[jahschwa]

*** Fatal error: duplicate @botcmd or @botfunc (see log) ***

2021-04-09 19:45:59 | sibylbot | INF | Loading plugin "library"
2021-04-09 19:45:59 | sibylbot | ERR | Error loading plugin "library"
2021-04-09 19:45:59 | sibylbot | ERR |   SyntaxError: invalid syntax
2021-04-09 19:45:59 | sibylbot | DEB | Traceback (most recent call last):
  File "/tripool/data/laptopdude/src/git/sibyl/lib/sibylbot.py", line 292, in __load_plugins
    mod = util.load_module(f,d)
  File "/tripool/data/laptopdude/src/git/sibyl/lib/util.py", line 335, in load_module
    return imp.load_module(name,*found)
  File "/usr/lib/python3.8/imp.py", line 234, in load_module
    return load_source(name, filename, file)
  File "/usr/lib/python3.8/imp.py", line 171, in load_source
    module = _load(spec)
  File "<frozen importlib._bootstrap>", line 702, in _load
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 779, in exec_module
  File "<frozen importlib._bootstrap_external>", line 916, in get_code
  File "<frozen importlib._bootstrap_external>", line 846, in source_to_code
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "cmds/library.py", line 241
    else:
    ^
SyntaxError: invalid syntax