Breaking change in markupsafe makes flask crash on service startup

[abrisan]

This issue in markupsafe is transitively included in flask, so even applications running Flask 1.1.4 are crashing on startup.

Here is a sample stack trace:

Traceback (most recent call last):
  File "/<...>/bin/superset", line 33, in <module>
    sys.exit(load_entry_point('apache-superset==1.4.1', 'console_scripts', 'superset')())
  File "/opt/bb/bin/superset", line 25, in importlib_load_entry_point
    return next(matches).load()
  File "/<...>/lib/python3.9/importlib/metadata.py", line 77, in load
    module = import_module(match.group('module'))
  File "/<...>/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 972, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 850, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "/<...>/lib/python3.9/site-packages/superset/__init__.py", line 18, in <module>
    from flask import current_app, Flask
  File "/<...>/lib/python3.9/site-packages/flask/__init__.py", line 14, in <module>
    from jinja2 import escape
  File "/<...>/lib/python3.9/site-packages/jinja2/__init__.py", line 12, in <module>
    from .environment import Environment
  File "/<...>/lib/python3.9/site-packages/jinja2/environment.py", line 25, in <module>
    from .defaults import BLOCK_END_STRING
  File "/<...>/lib/python3.9/site-packages/jinja2/defaults.py", line 3, in <module>
    from .filters import FILTERS as DEFAULT_FILTERS  # noqa: F401
  File "/<...>/lib/python3.9/site-packages/jinja2/filters.py", line 13, in <module>
    from markupsafe import soft_unicode
ImportError: cannot import name 'soft_unicode' from 'markupsafe' (/<...>/lib/python3.9/site-packages/markupsafe/__init__.py)

Environment:

• Python version: 3.9
• Flask version: 1.1.4

[davidism]

Duplicate of #4455

You are using an unsupported version of Flask and Jinja, please update to the latest version. Additionally, please read https://hynek.me/articles/semver-will-not-save-you/, then use a tool like pip-tools to pin your dependencies and control when you get updates. Be sure to run your tests with deprecation warnings treated as errors so that you get notified of these types of changes early.

[BenDavisson]

If you have a dependency on an older version of Flask like myself, I found a solution by following #4455 (comment) given by @fwindolf.

My versions:

- flask=1.1.4
- itsdangerous==1.1.0
- markupsafe==1.1.1