Idea to fix output when executing a command that fails.

[margueritepd]

Throwing this out here. This is to fix the output when an ssh command exits with non-zero status. The output currently is:

Blender::ExecutionFailed: #<File:0x00562760b79ca0>

With this change, the output would be the content of stderr.

Feedback I would like to get:

• Is using a tempfile instead of /dev/null crazy talk? Do the implications outweigh the benefits?
• How would I test this? Not clear from the code how I would stub the ssh command to return a non-zero exit code, without actually mocking the class under test.
• I would like to also output ~300 characters of standard out as part of raise ExecutionError, stderr when a command fails. Is that crazy talk?

If this PR seems reasonable, I will put up a different PR with tests, etc.

[ranjib]

:+1: once specs fixed.

[nickpegg]

You could use a StringIO instead of a temp file if you wanted to avoid touching disk.

:+1: Looks reasonable to me, but will be breaking behavior if anyone is relying on ExecOutput to have IOs for stdout/stderr.

[Sarah-E-Greene]

:+1: Seems like a good plan to me.

[ranjib]

@margueritepd i have pushed an example spec here: https://github.com/PagerDuty/blender/blob/readable_error_msg_spec/spec/blender/drivers/ssh_spec.rb#L19

[margueritepd]

I have a possibly better solution to this, closing now.