[CP] Pub: Properly handle case where the client is unable to fetch advisories

[sigurdm]

Commit(s) to merge

Landed in pub as dart-lang/pub@e05f76b
Rolled to sdk in https://dart-review.googlesource.com/c/sdk/+/370882

Target

stable

Prepared changelist for beta/stable

https://dart-review.googlesource.com/c/sdk/+/370885

Issue Description

When attempting to fetch advisories from a pub server, the client would crash if they were not available.

This breaks pub for mirrors of pub.dev that fail to proxy advisories.

What is the fix

Print a warning instead of crashing

Why cherry-pick

This impacts users of mirrors that have not been updated to mirror advisories - they are not able to get a resolution with pub.

Risk

Medium-low

Issue link(s)

dart-lang/pub#4269

Extra Info

No response

[mit-mit]

sgtm

[sigurdm]

cc @szakarias

[athomas]

Small change, good coverage, LGTM

[athomas]

Released in 3.4.4.