Solaar >= 1.1.2 requires python >= 3.8

Created by: Kieltux

Information Running solaar 1.1.2 on python < 3.8 does not work, but documentation says: requires Python 3.7+ and requires several packages to be installed

# solaar   
Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/solaar/i18n.py", line 63, in <module>
    unicode  # noqa: F821
NameError: name 'unicode' is not defined

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/solaar", line 54, in <module>
    import solaar.gtk
  File "/usr/lib/python3.6/site-packages/solaar/gtk.py", line 29, in <module>
    import solaar.i18n as _i18n
  File "/usr/lib/python3.6/site-packages/solaar/i18n.py", line 69, in <module>
    pgettext = _gettext.pgettext
AttributeError: module 'gettext' has no attribute 'pgettext'

Describe the bug The attribute 'pgettext' is added to gettext with python 3.8.

See: https://docs.python.org/3/whatsnew/3.8.html gettext¶ Added pgettext() and its variants. (Contributed by Franz Glasner, Éric Araujo, and Cheryl Sabella in bpo-2504.)