Mitmproxy won't start due to soft_unicode removed from markupsafe

[noseka1]

After building the debug image and trying to run it, the mitproxy would fail to start:

Traceback (most recent call last): File "/usr/bin/mitmweb", line 8, in sys.exit(mitmweb()) File "/usr/lib/python3.8/site-packages/mitmproxy/tools/_main.py", line 172, in mitmweb from mitmproxy.tools import web File "/usr/lib/python3.8/site-packages/mitmproxy/tools/web/init.py", line 1, in from mitmproxy.tools.web import master File "/usr/lib/python3.8/site-packages/mitmproxy/tools/web/master.py", line 5, in from mitmproxy import addons File "/usr/lib/python3.8/site-packages/mitmproxy/addons/init.py", line 12, in from mitmproxy.addons import onboarding File "/usr/lib/python3.8/site-packages/mitmproxy/addons/onboarding.py", line 2, in from mitmproxy.addons.onboardingapp import app File "/usr/lib/python3.8/site-packages/mitmproxy/addons/onboardingapp/init.py", line 3, in from flask import Flask, render_template File "/usr/lib/python3.8/site-packages/flask/init.py", line 14, in from jinja2 import escape File "/usr/lib/python3.8/site-packages/jinja2/init.py", line 12, in from .environment import Environment File "/usr/lib/python3.8/site-packages/jinja2/environment.py", line 25, in from .defaults import BLOCK_END_STRING File "/usr/lib/python3.8/site-packages/jinja2/defaults.py", line 3, in from .filters import FILTERS as DEFAULT_FILTERS # noqa: F401 File "/usr/lib/python3.8/site-packages/jinja2/filters.py", line 13, in from markupsafe import soft_unicode ImportError: cannot import name 'soft_unicode' from 'markupsafe' (/usr/lib/python3.8/site-packages/markupsafe/init.py)

Fixed the issue by explicitly requiring an older version of MarkupSafe.

The issue is related to: https://github.com/pallets/markupsafe/issues/282