update requirements to django 3.2

I tried to run docker build and go this:
Building wheels for collected packages: pretix
  Building wheel for pretix (setup.py): started
  Building wheel for pretix (setup.py): finished with status 'error'
  error: subprocess-exited-with-error

  × python setup.py bdist_wheel did not run successfully.
  │ exit code: 1
  ╰─> [48 lines of output]
      running bdist_wheel
      running build
      Traceback (most recent call last):
        File "<string>", line 2, in <module>
        File "<pip-setuptools-caller>", line 34, in <module>
        File "/pretix/src/setup.py", line 91, in <module>
          setup(
        File "/usr/local/lib/python3.8/site-packages/setuptools/__init__.py", line 104, in setup
          return distutils.core.setup(**attrs)
        File "/usr/local/lib/python3.8/site-packages/setuptools/_distutils/core.py", line 184, in setup
          return run_commands(dist)
        File "/usr/local/lib/python3.8/site-packages/setuptools/_distutils/core.py", line 200, in run_commands
          dist.run_commands()
        File "/usr/local/lib/python3.8/site-packages/setuptools/_distutils/dist.py", line 969, in run_commands
          self.run_command(cmd)
        File "/usr/local/lib/python3.8/site-packages/setuptools/dist.py", line 967, in run_command
          super().run_command(command)
        File "/usr/local/lib/python3.8/site-packages/setuptools/_distutils/dist.py", line 988, in run_command
          cmd_obj.run()
        File "/usr/local/lib/python3.8/site-packages/wheel/bdist_wheel.py", line 368, in run
          self.run_command("build")
        File "/usr/local/lib/python3.8/site-packages/setuptools/_distutils/cmd.py", line 316, in run_command
          self.distribution.run_command(command)
        File "/usr/local/lib/python3.8/site-packages/setuptools/dist.py", line 967, in run_command
          super().run_command(command)
        File "/usr/local/lib/python3.8/site-packages/setuptools/_distutils/dist.py", line 988, in run_command
          cmd_obj.run()
        File "/pretix/src/setup.py", line 63, in run
          django.setup()
        File "/usr/local/lib/python3.8/site-packages/django/__init__.py", line 24, in setup
          apps.populate(settings.INSTALLED_APPS)
        File "/usr/local/lib/python3.8/site-packages/django/apps/registry.py", line 114, in populate
          app_config.import_models()
        File "/usr/local/lib/python3.8/site-packages/django/apps/config.py", line 301, in import_models
          self.models_module = import_module(models_module_name)
        File "/usr/local/lib/python3.8/importlib/__init__.py", line 127, in import_module
          return _bootstrap._gcd_import(name[level:], package, level)
        File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
        File "<frozen importlib._bootstrap>", line 991, in _find_and_load
        File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
        File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
        File "<frozen importlib._bootstrap_external>", line 843, in exec_module
        File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
        File "/pretix/src/pretix/base/models/__init__.py", line 4, in <module>
          from .checkin import Checkin, CheckinList
        File "/pretix/src/pretix/base/models/checkin.py", line 8, in <module>
          from jsonfallback.fields import FallbackJSONField
      ModuleNotFoundError: No module named 'jsonfallback'
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
  ERROR: Failed building wheel for pretix
  Running setup.py clean for pretix
Failed to build pretix
ERROR: Could not build wheels for pretix, which is required to install pyproject.toml-based projects
The command '/bin/sh -c cd /pretix/src && pip3 install .' returned a non-zero code: 1
It seems some wheel problem, maybe from dependencies? I didn't have more time to look into it, does this happens to you?
fossasia / eventyay-tickets

update requirements to django 3.2 #75
