pkgsite: doesn't handle non-ascii package name, regression compared to godoc

[maruel]

Discovered while investigating #43035 :

pkg.go.dev fails at loading a non-ascii package name https://pkg.go.dev/github.com/maruel/panicparse/v2/cmd/panic/internal/%C3%B9tf8
but godoc succeeds: https://godoc.org/github.com/maruel/panicparse/cmd/panic/internal/%c3%b9tf8

Feels like a regression to me. @julieqiu

[julieqiu]

Marking this as WaitingForInfo on #43035. Pkg.go.dev currently skips import paths that don't pass module.CheckImportPath.

[maruel]

Since #43035 is WAI and there's going to be a release note as per #43052, you can mark it WAI. Maybe worth pinging Bryan to clarify that pkg.go.dev enforces this too.

[julieqiu]

SGTM - closing as WAI.

/cc @bcmills @jayconrod @matloob