[WIP] Fix fetch-lib error in charmcraft 3.4.3

[Copilot]

• Explore repository structure and understand the issue
• Identify the bug location (line 1539 and 1562 in charmcraft/application/commands/store.py)
• Confirm bug exists in 4.0.1, hotfix/3.5, and main branches
• Write a failing test that reproduces the issue
• Implement the fix for both error locations
• Run the test on tag 4.0.1 to verify it fails
• Run the test on hotfix/3.5 to verify it fails
• Run the test on hotfix/2.7 to verify behavior (command may not exist)
• Run the test on main to verify it fails without fix
• Verify the fix works with the tests
• Run code review and CodeQL checks

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[3.4.3] Charmcraft fetch-lib fails with Library None not found in Charmhub.</issue_title>
<issue_description>### Bug Description

I am using charmcraft: installed: 3.4.3.post51+g6153055c (6228) 60MB classic
Installed from channel latest/edge

We have done some few changes in the OpenSearch libs and now the check_libs started failing with an error instead of simply a list of outdated libs.

Running it locally and I can also reproduce the same error.

This error message is not really helpful and the logs print the entire lib content, making it hard to read.

To Reproduce

$ git clone https://github.com/canonical/opensearch-operator -b 2/edge
$ cd opensearch-operator
$ charmcraft fetch-lib
Library None not found in Charmhub.

Environment

OS: 24.04
charmcraft: latest/edge, currently on 3.4.3

charmcraft.yaml

# Copyright 2022 Canonical Ltd.
# See LICENSE file for licensing details.

type: charm
platforms:
  ubuntu@22.04:amd64:
  ubuntu@24.04:amd64:
# Files implicitly created by charmcraft without a part:
# - dispatch (https://github.com/canonical/charmcraft/pull/1898)
# - manifest.yaml
#   (https://github.com/canonical/charmcraft/blob/9ff19c328e23b50cc06f04e8a5ad4835740badf4/charmcraft/services/package.py#L259)
# Files implicitly copied/"staged" by charmcraft without a part:
# - actions.yaml, config.yaml, metadata.yaml
#   (https://github.com/canonical/charmcraft/blob/9ff19c328e23b50cc06f04e8a5ad4835740badf4/charmcraft/services/package.py#L290-L293
#   https://github.com/canonical/charmcraft/blob/9ff19c328e23b50cc06f04e8a5ad4835740badf4/charmcraft/services/package.py#L156-L157)
parts:
  # "poetry-deps" part name is a magic constant
  # https://github.com/canonical/craft-parts/pull/901
  poetry-deps:
    plugin: nil
    build-packages:
      - curl
    override-build: |
      # Use environment variable instead of `--break-system-packages` to avoid failing on older
      # versions of pip that do not recognize `--break-system-packages`
      # `--user` needed (in addition to `--break-system-packages`) for Ubuntu >=24.04
      PIP_BREAK_SYSTEM_PACKAGES=true python3 -m pip install --user --upgrade pip==24.3.1  # renovate: charmcraft-pip-latest

      # Use uv to install poetry so that a newer version of Python can be installed if needed by poetry
      curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/uv/releases/download/0.5.15/uv-installer.sh | sh  # renovate: charmcraft-uv-latest
      # poetry 2.0.0 requires Python >=3.9
      if ! "$HOME/.local/bin/uv" python find '>=3.9'
      then
        # Use first Python version that is >=3.9 and available in an Ubuntu LTS
        # (to reduce the number of Python versions we use)
        "$HOME/.local/bin/uv" python install 3.10.12  # renovate: charmcraft-python-ubuntu-22.04
      fi
      "$HOME/.local/bin/uv" tool install --no-python-downloads --python '>=3.9' poetry==2.0.0 --with poetry-plugin-export==1.8.0  # renovate: charmcraft-poetry-latest

      ln -sf "$HOME/.local/bin/poetry" /usr/local/bin/poetry
  # "charm-poetry" part name is arbitrary; use for consistency
  # Avoid using "charm" part name since that has special meaning to charmcraft
  charm-poetry:
    # By default, the `poetry` plugin creates/stages these directories:
    # - lib, src
    #   (https://github.com/canonical/charmcraft/blob/9ff19c328e23b50cc06f04e8a5ad4835740badf4/charmcraft/parts/plugins/_poetry.py#L76-L78)
    # - venv
    #   (https://github.com/canonical/charmcraft/blob/9ff19c328e23b50cc06f04e8a5ad4835740badf4/charmcraft/parts/plugins/_poetry.py#L95
    #   https://github.com/canonical/craft-parts/blob/afb0d652eb330b6aaad4f40fbd6e5357d358de47/craft_parts/plugins/base.py#L270)
    plugin: poetry
    source: .
    after:
      - poetry-deps
    poetry-export-extra-args: ['--only', 'main,charm-libs']
    build-packages:
      - libffi-dev  # Needed to build Python dependencies with Rust from source
      - libssl-dev  # Needed to build Python dependencies with Rust from source
      - pkg-config  # Needed to build Python dependencies with Rust from source
    override-build: |
      # Workaround for https://github.com/canonical/charmcraft/issues/2068
      # rustup used to install rustc and cargo, which are needed to build Python dependencies with Rust from source
      if [[ "$CRAFT_PLATFORM" == ubuntu@20.04:* || "$CRAFT_PLATFORM" == ubuntu@22.04:* ]]
      then
        snap install rustup --classic
      else
        apt-get install rustup -y
      fi

      # If Ubuntu version < 24.04, rustup was installed from snap instead of from the Ubuntu
      # archive—which means the rustup version could be updated at any time. Print rustup version
      # to build log to make changes to the snap's rustup version easier to track
      rustup --version

      # rpds-py (Python package) >=0.19.0 requires rustc >=1.76, which is not available in the...

</details>

- Fixes canonical/charmcraft#2204

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