Improve experience when system does not have PortAudio installed yet

[matchu]

When I tried to use pymusiclooper for the first time, I ran into a confusing error message on playback:

ERROR    module 'sounddevice' has no attribute 'OutputStream'

To debug, I ran ~/.local/pipx/venvs/pymusiclooper/bin/python, and tried importing the sounddevice library, and got this clearer error message:

>>> import sounddevice
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/matchu/.local/pipx/venvs/pymusiclooper/lib/python3.10/site-packages/sounddevice.py", line 71, in <module>
    raise OSError('PortAudio library not found')
OSError: PortAudio library not found

Researching a bit, it looks like the lazy-loader library imports modules in a slightly complex way, which happens to not raise import side-effects like this one.

So, in this PR, I've made two changes:

1. Add instructions to the README to help Linux users understand that they may need to install PortAudio, and how to do it.
2. Replace the lazy-loader call with our own simple hand-written lazy-loader function for sounddevice, which will raise the more helpful error message if the user is missing PortAudio.

Thank you for this tool! I hope this is helpful.

Summary by Sourcery

Improve user experience by providing clearer error messages when PortAudio is not installed and update documentation to guide Linux users on installing PortAudio.

Enhancements:

• Replace the 'lazy-loader' call with a custom lazy-loader function for 'sounddevice' to provide clearer error messages when dependencies like PortAudio are missing.

Documentation:

• Add instructions to the README for Linux users on how to install the PortAudio library if needed.

[sourcery-ai]

Reviewer's Guide by Sourcery

The PR improves the user experience when PortAudio is not installed by implementing a custom lazy-loading mechanism for the sounddevice module and adding installation instructions. The changes replace the existing lazy-loader library with a hand-written lazy-loading function that provides clearer error messages when PortAudio dependencies are missing.

Class diagram for PlaybackHandler with custom lazy-loader

classDiagram
    class PlaybackHandler {
        - stream
        + __init__()
        + start_playback()
        + stop_playback()
    }
    class sd {
        + CallbackStop()
        + OutputStream()
    }
    class importlib {
        + import_module()
    }
    PlaybackHandler --> sd : uses
    PlaybackHandler --> importlib : uses
    note for sd "Custom lazy-loader function replaces lazy-loader library"

Loading

File-Level Changes

Change	Details	Files
Implement custom lazy-loading mechanism for sounddevice module	Remove lazy-loader library dependency for sounddevice Add custom lazy-loading function using importlib Update sounddevice module access to use the new lazy-loading function Modify stream creation and callback to use the lazy-loaded module	pymusiclooper/playback.py
Add PortAudio installation instructions for Linux users	Add note about PortAudio requirement for the play command on Linux Include Ubuntu-specific installation command for libportaudio2	README.md

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[sourcery-ai]

Hey @matchu - I've reviewed your changes and they look great!

Here's what I looked at during the review

• 🟢 General issues: all looks good
• 🟢 Security: all looks good
• 🟢 Testing: all looks good
• 🟢 Complexity: all looks good
• 🟢 Documentation: all looks good

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