[Bug 2024325] Re: [SRU] trac crashes while importing a library in Ubuntu 20.04 (ImportError: cannot import name 'soft_unicode' from 'jinja2.utils')

[Robie Basak]

This looks good. Thanks!

I added a line to "Where problems could occur".

I suggest changing the changelog entry to simply:

  * Fix crash on startup (LP: #2024325).

Saying that we backported the fix seems superfluous to me. The people
who read this are likely to be non-technical, and those technical can
always review the diff and/or dep3 headers to understand the code
changes if they're interested. But what we do want to do is make it
clear to users that we are actually fixing the bug that they have
experienced. "error with library import" sounds like something that
could just be an edge case and describes the root cause that the user
might not know as opposed to the actual user experience. "crash on
startup" makes it clear that if a user was affected by that then that's
what we're addressing by this fix.

Please let me know if you're OK with this fix and I'll go ahead and
sponsor. After that, it will await review by the SRU team.

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https://bugs.launchpad.net/bugs/2024325

Title:
  [SRU] trac crashes while importing a library in Ubuntu 20.04
  (ImportError: cannot import name 'soft_unicode' from 'jinja2.utils')

Status in trac package in Ubuntu:
  Fix Released
Status in trac source package in Jammy:
  Confirmed

Bug description:
  [ Impact ]

  trac is completely unusable as it will fail with the below error
  whenever any user tries to run "tracd" or "trac-admin":

  Traceback (most recent call last):
    File "/usr/bin/tracd", line 33, in <module>
      sys.exit(load_entry_point('Trac==1.5.3', 'console_scripts', 'tracd')())
    File "/usr/bin/tracd", line 25, in importlib_load_entry_point
      return next(matches).load()
    File "/usr/lib/python3.10/importlib/metadata/__init__.py", line 171, in load
      module = import_module(match.group('module'))
    File "/usr/lib/python3.10/importlib/__init__.py", line 126, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
    File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
    File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
    File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
    File "<frozen importlib._bootstrap_external>", line 883, in exec_module
    File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
    File "/usr/lib/python3/dist-packages/trac/web/standalone.py", line 35, in <module>
      from trac.web.auth import BasicAuthentication, DigestAuthentication
    File "/usr/lib/python3/dist-packages/trac/web/auth.py", line 29, in <module>
      from trac.web.chrome import Chrome, INavigationContributor
    File "/usr/lib/python3/dist-packages/trac/web/chrome.py", line 40, in <module>
      from trac.mimeview.api import RenderingContext, get_mimetype
    File "/usr/lib/python3/dist-packages/trac/mimeview/__init__.py", line 14, in <module>
      from trac.mimeview.api import *
    File "/usr/lib/python3/dist-packages/trac/mimeview/api.py", line 70, in <module>
      from trac.resource import Resource
    File "/usr/lib/python3/dist-packages/trac/resource.py", line 21, in <module>
      from trac.util.presentation import classes
    File "/usr/lib/python3/dist-packages/trac/util/presentation.py", line 26, in <module>
      from jinja2.utils import soft_unicode
  ImportError: cannot import name 'soft_unicode' from 'jinja2.utils' (/usr/lib/python3/dist-packages/jinja2/utils.py)

  [ Test Plan ]

  * Simple test:
    - Execute "tracd --help" or "tracd"
    - Execute "trac-admin --help" or "trac-admin"
    - If its not fixed then both the commands will fail as the error above
    - With fixed package both the commands will show the help message.

  * More comprehensive test: (execue the following as root)
    - mkdir -p /var/lib/trac
    - trac-admin /var/lib/trac/myproject initenv
    - Enter some project name when prompted
    - Leave default sqlite DB (just press enter)
    - echo -n "tracadmin:example.com:" > /var/lib/trac/myproject/users.htdigest
    - trac-admin /var/lib/trac/myproject permission add tracadmin TRAC_ADMIN
    - tracd --port 8080 --auth=*,/var/lib/trac/myproject/users.htdigest,example.com /var/lib/trac/myproject
    - open http://127.0.0.1:8080 in browser, it should show the project name and clicking on that should show the welcome screen

  [ Where problems could occur ]

  It is not changing any part of the code, its only importing the module
  with the new name and so there is minimum chance of any regression.

  [racb] We're adjusting imports of soft_unicode/soft_str. Problems
  might manifest in module imports, or in the assumption that one of
  these is an exact replacement of the other.

  [ Other Info ]

  - The Ubuntu patch is a combination of portions of two upstream but related changes.
  - One of the upstream changes mentions about an AssertionError for jinja, so it will be great if this can be tested by a real user of trac. The testplan only checks the server starts and is working.

  [ Original Bug Description ]

  Trac 1.5.3 which comes with Ubuntu 20.04 crashes because of problems
  with a library. The problem was fixed upstream:
  https://trac.edgewall.org/ticket/13404

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