Handle missing example files gracefully

[chadwhitacre]

We're seeing a bit of noise in our dogfooding instance from cases where it seems folks have mucked with the example files we expect to exist. Let's give a more specific error message in this case and avoid reporting to dogfooding.

[chadwhitacre]

Expecting e186a79 to fail with a generic error.

[chadwhitacre]

https://github.com/getsentry/self-hosted/actions/runs/4067040190/jobs/7003897054#step:5:173

Ensuring Relay credentials ...
  Creating ../relay/config.yml...
  cp: cannot stat '../relay/config.example.yml': No such file or directory
  Error in ./install/_lib.sh:48.
  'cp -n $(echo "$1" | sed 's/\.[^.]*$/.example&/') "$1"' exited with status 1
  yes: standard output: Broken pipe
  yes: standard output: Broken pipe
  yes: standard output: Broken pipe
  -> ./install.sh:main:26
  --> ensure-relay-credentials.sh:source:6
  ---> ./install/_lib.sh:ensure_file_from_example:48

[chadwhitacre]

I confirmed that an exit in a function exits the whole script, with default 0 ofc.

[chadwhitacre]

Getting the "Oops!" but the test is still red. 🤔

https://github.com/getsentry/self-hosted/actions/runs/4067238068/jobs/7004344020#step:5:174

[chadwhitacre]

Yeah okay so install.sh is exiting cleanly and proceeding to run.sh.

self-hosted/.github/workflows/test.yml

Lines 74 to 75 in be48754

	- name: Integration Test
	run: ./integration-test.sh

self-hosted/integration-test.sh

Lines 9 to 11 in be48754

	echo "Testing initial install"
	./install.sh
	./_integration-test/run.sh

  Oops! Where did ../relay/config.example.yml go? 🤨 We need it in order to create ../relay/config.yml.
  + ./_integration-test/run.sh

https://github.com/getsentry/self-hosted/actions/runs/4067238068/jobs/7004344020#step:5:175

If install.sh exits with > 0 I bet run.sh won't be called due to ...

self-hosted/integration-test.sh

Line 2 in be48754

set -ex

[chadwhitacre]

Testing in e977937 ...

[chadwhitacre]

I'm expecting to see the "Oops!" and then the integration-test.sh terminates.

[chadwhitacre]

Boom!

  Oops! Where did ../relay/config.example.yml go? 🤨 We need it in order to create ../relay/config.yml.
  Error: Process completed with exit code 42.
  ##[debug]Finishing: Integration Test

Okay, ready for review.