Current testing branch is broken

[severinsimmler]

Can you reproduce this?

$ python topicsexplorer.py 
 * Serving Flask app "topicsexplorer" (lazy loading)
 * Environment: production
   WARNING: Do not use the development server in a production environment.
   Use a production WSGI server instead.
 * Debug mode: on
Traceback (most recent call last):
  File "/home/severin/git/TopicsExplorer/application/gui.py", line 56, in run
    self.application.run(port=self.port, debug=True)
  File "/home/severin/.local/share/virtualenvs/TopicsExplorer-dn_JGKYt/lib/python3.6/site-packages/flask/app.py", line 943, in run
    run_simple(host, port, self, **options)
  File "/home/severin/.local/share/virtualenvs/TopicsExplorer-dn_JGKYt/lib/python3.6/site-packages/werkzeug/serving.py", line 812, in run_simple
    reloader_type)
  File "/home/severin/.local/share/virtualenvs/TopicsExplorer-dn_JGKYt/lib/python3.6/site-packages/werkzeug/_reloader.py", line 267, in run_with_reloader
    signal.signal(signal.SIGTERM, lambda *args: sys.exit(0))
  File "/usr/lib/python3.6/signal.py", line 47, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
ValueError: signal only works in main thread
Received signal 6
#0 0x7ff9693a552f <unknown>
#1 0x7ff967dd6b1d <unknown>
#2 0x7ff9693a5a3e <unknown>
#3 0x7ff98a451100 <unknown>
#4 0x7ff98a451077 gsignal
#5 0x7ff98a432535 abort
#6 0x7ff972f373bc QMessageLogger::fatal()
#7 0x7ff96fcd14ce pyqt5_err_print()
#8 0x7ff96ffd8b6d sip_api_call_procedure_method
#9 0x7ff96fca12c3 sipQThread::run()
#10 0x7ff972f63564 QThreadPrivate::start()
#11 0x7ff98a3f7164 start_thread
#12 0x7ff98a52adef clone
  r8: 0000000000000000  r9: 00007ff94a7389b0 r10: 0000000000000008 r11: 0000000000000246
 r12: 00007ff9380492b0 r13: 00007ff938049670 r14: 00007ff98903d0d8 r15: 00007ff920434b20
  di: 0000000000000002  si: 00007ff94a7389b0  bp: 00007ff92033eaf8  bx: 00007ff94a738d10
  dx: 0000000000000000  ax: 0000000000000000  cx: 00007ff98a451077  sp: 00007ff94a7389b0
  ip: 00007ff98a451077 efl: 0000000000000246 cgf: 002b000000000033 erf: 0000000000000000
 trp: 0000000000000000 msk: 0000000000000000 cr2: 0000000000000000
[end of stack trace]
Calling _exit(1). Core file will not be generated.