Gracefully handle Spotify API errors

[arsaboo]

Description

Fixes #4942

To Do

• Documentation. (If you've add a new command-line flag, for example, find the appropriate page under docs/ to describe it.)
• Changelog. (Add an entry to docs/changelog.rst near the top of the document.)
• Tests. (Encouraged but not strictly required.)

[sampsyo]

Hey, thanks for getting a fix for this started!!

If possible, what do you think about breaking this into a couple of steps? There's a first, more basic thing we can do here to just handle the exceptions—and then a separate, more complex matter of adding a new retry loop. The latter thing might require some care—and, in fact, there is another way to do it without implementing our own loop. (If we do the looping on our end, it might be nice to reuse the current recursive strategy rather than a for loop? Not sure.) Would it be OK with you to start with only the first thing (the extra exception handlers) and merge that before adding retries?

Namely, these exceptions could also possibly just raise SpotifyAPIError exceptions, which already cause the plugin to harmlessly log an error and move on with its life:

beets/beetsplug/spotify.py

Lines 406 to 408 in e10b955

	except SpotifyAPIError as e:
	self._log.debug('Spotify API error: {}', e)
	return []

Even when retries expire, this might be a friendlier thing to do than to crash with a UserError.

[arsaboo]

@sampsyo I have removed the retry logic in this PR. However, we need to fix that soon. I am increasingly seeing the Retry-After interval not being returned in the exception.

Also, are you completely opposed to the while loop for the retry logic? Using the approach you linked will require us to change the plugin to use request sessions, which we are not doing currently.

[sampsyo]

Awesome! Thank you for rearranging this; this all looks right to me.

No, I'm definitely not opposed to replacing recursion with iteration for the retry loop. I just hope to be able to think carefully about both concerns separately.