apt_dpkg: discard cached contents mapping on OSError

[bdrung]

test_retrace_jammy_sandbox might fail in a autopkgtest VM:

Traceback (most recent call last):
  File "/usr/bin/apport-retrace", line 713, in <module>
    sys.exit(main(sys.argv[1:]))
             ~~~~^^^^^^^^^^^^^^
  File "/usr/bin/apport-retrace", line 542, in main
    sandbox, cache, outdated_msg = apport.sandboxutils.make_sandbox(
                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        report,
        ^^^^^^^
    ...<6 lines>...
        options.dynamic_origins,
        ^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/usr/lib/python3/dist-packages/apport/sandboxutils.py", line 274, in make_sandbox
    pkgs = needed_runtime_packages(report, pkgmap_cache_dir, pkg_versions, verbose)
  File "/usr/lib/python3/dist-packages/apport/sandboxutils.py", line 103, in needed_runtime_packages
    pkg = packaging.get_file_package(
        line,
    ...<3 lines>...
        arch=report.get("Architecture"),
    )
  File "/usr/lib/python3/dist-packages/apport/packaging_impl/apt_dpkg.py", line 800, in get_file_package
    return self._search_contents(file, map_cachedir, release, arch)
           ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/apport/packaging_impl/apt_dpkg.py", line 1752, in _search_contents
    contents_mapping = self._get_file2pkg_mapping(map_cachedir, release, arch)
  File "/usr/lib/python3/dist-packages/apport/packaging_impl/apt_dpkg.py", line 1726, in _get_file2pkg_mapping
    file2pkg = self._contents_mapping(map_cachedir, release, arch)
  File "/usr/lib/python3/dist-packages/apport/packaging_impl/apt_dpkg.py", line 340, in _contents_mapping
    self._contents_mapping_obj = pickle.load(fp)
                                 ~~~~~~~~~~~^^^^
EOFError: Ran out of input

Discard the cache in those cases and just rebuild them.

Bug: https://launchpad.net/bugs/2149911

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.47%. Comparing base (5beb93d) to head (97ccb24).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #593      +/-   ##
==========================================
+ Coverage   84.45%   84.47%   +0.02%     
==========================================
  Files         104      104              
  Lines       20939    20967      +28     
  Branches     3212     3216       +4     
==========================================
+ Hits        17683    17711      +28     
- Misses       2815     2816       +1     
+ Partials      441      440       -1     

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