cmd/go: misleading error from 'go list -versions' when GOPROXY is invalid #32335
Description
Observed:
example.com$ gotip version
go version devel +220552f6 Thu May 30 17:59:57 2019 +0000 linux/amd64
example.com$ gotip mod init example.com
go: creating new go.mod: module example.com
example.com$ GOPROXY='' gotip list -versions -m rsc.io/quote
go: finding rsc.io/quote v1.5.2
rsc.io/quote v1.0.0 v1.1.0 v1.2.0 v1.2.1 v1.3.0 v1.4.0 v1.5.0 v1.5.1 v1.5.2 v1.5.3-pre1
example.com$ GOPROXY='bogus-path' gotip list -versions -m rsc.io/quote
go list -m rsc.io/quote: module "rsc.io/quote" is not a known dependency
example.com$ GOPROXY='bogus-path' gotip get rsc.io/quote@latest
go get rsc.io/quote@latest: invalid proxy URL missing scheme: bogus-path
example.com$
Expected:
An error message from list similar to the one from get:
example.com$ GOPROXY='bogus-path' gotip list -versions -m rsc.io/quote
go list -m rsc.io/quote: invalid proxy URL missing scheme: bogus-path