amypet.web requires `TKinter` module

[jhuguetn]

Failed to run the web UI version of AmyPET. Looks like an additional package named TKinter is needed. TKinter is a Python interface to the Tcl/Tk toolkit. See trace below,

(amypet_dev) user@host:/.../tmp/amypet$ pip install amypet[web] --quiet

(amypet_dev) user@host:/.../tmp/amypet$ amypet.web
Traceback (most recent call last):
  File "/home/user/venvs/amypet_dev/bin/amypet.web", line 5, in <module>
    from amypet.web import main
  File "/home/user/venvs/amypet_dev/lib/python3.7/site-packages/amypet/web.py", line 3, in <module>
    from . import _backend_web
  File "/home/user/venvs/amypet_dev/lib/python3.7/site-packages/amypet/_backend_web.py", line 4, in <module>
    import tkinter as tk
ModuleNotFoundError: No module named 'tkinter'

I can confirm error can be suppressed by installing the missing module as follows,

apt-get install python3-tk

If such module is a requirement I would suggest noting it in the README file.

[casperdcl]

Unfortunately folder selection isn't possible in web browsers (only file selection is possible) so yes we do indeed need tkinter.

Again not really a problem in conda but yes needs mentioning in other systems.