internal/e2e: tweak how we use secret env vars
Only require GITHUB_TOKEN when a script calls create-github-token.
This allows other tests which don't require github auth to be run
on their own via `go test -run` without having to set this secret.
The failure is now done via t.Fatal instead of panic,
and the env var is only passed along for `git push` via the builtin.
Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: I54d7822938cea7d1c1c66b9f7849e60b680e5342
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1171910
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Roger Peppe <rogpeppe@gmail.com>