`UnSolvable.explain_problems()` fails if the conflict involves a pinned package and the request has `flags.allow_uninstall=False`

[jaimergp]

Troubleshooting docs

• [X] My problem is not solved in the Troubleshooting docs

Anaconda default channels

• [X] I do NOT use the Anaconda default channels (pkgs/* etc.)

How did you install Mamba?

Mambaforge or latest Miniforge

Search tried in issue tracker

Found invalid version predicate in

Latest version of Mamba

• [X] My problem is not solved with the latest version

Tried in Conda?

Not applicable

Describe your issue

If a conflict involves a pinned package (e.g. python) and flags.allow_uninstall=False, unsolvable.explain_problems() fails with libmambapy.bindings.specs.ParseError: Found invalid version predicate in "on python".

Reproducer with Python

```python import libmambapy db = libmambapy.solver.libsolv.Database( libmambapy.specs.ChannelResolveParams( channel_alias=libmambapy.specs.CondaURL.parse("https://conda.anaconda.org") ) ) print("loading repodata") repos = [ db.add_repo_from_repodata_json( path="/opt/conda/pkgs/cache/d9d93fba.json", # taken from the pkgs/cache url="https://conda.anaconda.org/conda-forge/linux-aarch64", channel_id="conda-forge", ), db.add_repo_from_repodata_json( path="/opt/conda/pkgs/cache/09cdf8bf.json", # taken from the pkgs/cache url="https://conda.anaconda.org/conda-forge/noarch", channel_id="conda-forge", ), ] Request = libmambapy.solver.Request MatchSpec = libmambapy.specs.MatchSpec print("crafting request...") request = Request( jobs=[ Request.Pin(MatchSpec.parse("python=3.12")), Request.Install(MatchSpec.parse("numpy=*=*py27*")), ], flags=Request.Flags( allow_downgrade=True, allow_uninstall=False, force_reinstall=False, keep_dependencies=True, keep_user_specs=True, order_request=False, # we do this ourselves strict_repo_priority=True, ), ) print("solving...") solver = libmambapy.solver.libsolv.Solver() outcome = solver.solve(db, request) if isinstance(outcome, libmambapy.solver.libsolv.UnSolvable): print(outcome.explain_problems(db, libmambapy.Palette.no_color())) else: print("OK!") ```

mamba info / micromamba info

libmamba version : 2.0.0
          mamba version : 2.0.0
           curl version : libcurl/8.7.1 OpenSSL/3.2.1 zlib/1.2.13 zstd/1.5.5 libssh2/1.11.0 nghttp2/1.58.0
     libarchive version : libarchive 3.7.2 zlib/1.2.13 liblzma/5.2.6 bz2lib/1.0.8 liblz4/1.9.3 libzstd/1.5.5
       envs directories : /root/.local/share/mamba/envs
          package cache : /root/.local/share/mamba/pkgs
                          /root/.mamba/pkgs
            environment : /opt/conda (active)
           env location : /opt/conda
      user config files : /root/.mambarc
 populated config files : /opt/conda/.condarc
       virtual packages : __unix=0=0
                          __linux=5.15.49=0
                          __glibc=2.31=0
                          __archspec=1=aarch64
               channels : https://conda.anaconda.org/conda-forge/linux-aarch64
                          https://conda.anaconda.org/conda-forge/noarch
       base environment : /root/.local/share/mamba
               platform : linux-aarch64

Logs

No response

environment.yml

No response

~/.condarc

No response