Require python-bugzilla

[hroncok]

Otherwise you'll get:

$ PYTHONPATH=. python -m portingdb serve
Traceback (most recent call last):
  File "/usr/lib64/python3.8/runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib64/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File ".../portingdb/portingdb/__main__.py", line 1, in <module>
    from portingdb.cli import main
  File ".../portingdb/portingdb/cli.py", line 11, in <module>
    from portingdb.check_fti import check_fti
  File ".../portingdb/portingdb/check_fti.py", line 11, in <module>
    import bugzilla
ModuleNotFoundError: No module named 'bugzilla'

[encukou]

Looks reasonable; thanks!