verdi computer test: fix bug in spurious output test

[sphuber]

Fixes #4314

The test that checks for spurious output when executing a normal command
on a computer over the transport had a bug in it that went unnoticed
because the code path was not tested. If the stderr of the command
contained any output the command would raise because the test that is
called _computer_test_no_unexpected_output would incorrectly return a
tuple of length one instead of two in that case.

In addition to adding tests to hit this code path, the message that is
printed in the case of non-empty stdout or stderr is deduplicated and
adapted to be bit clearer and refer directly to the documentation
instead of through a Github issue.

[codecov]

Codecov Report

Merging #4316 into develop will increase coverage by 0.07%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #4316      +/-   ##
===========================================
+ Coverage    79.04%   79.10%   +0.07%     
===========================================
  Files          468      468              
  Lines        34610    34611       +1     
===========================================
+ Hits         27354    27376      +22     
+ Misses        7256     7235      -21     

Flag	Coverage Δ
#django	72.72% <100.00%> (+0.06%)	⬆️
#sqlalchemy	71.91% <100.00%> (+0.07%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
aiida/cmdline/commands/cmd_computer.py	80.88% <100.00%> (+1.98%)	⬆️
aiida/transports/plugins/local.py	81.29% <0.00%> (+0.26%)	⬆️
aiida/transports/transport.py	63.68% <0.00%> (+0.45%)	⬆️
aiida/engine/daemon/client.py	73.57% <0.00%> (+1.15%)	⬆️
aiida/schedulers/plugins/direct.py	59.07% <0.00%> (+5.85%)	⬆️

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[ramirezfranciscof]

So, this is just 100% hunch, but where you are defining the exec_command_wait in each test, shouldn't one of those have the stdout/stderr and the empty string be switched?

[sphuber]

So, this is just 100% hunch, but where you are defining the exec_command_wait in each test, shouldn't one of those have the stdout/stderr and the empty string be switched?

It absolutely should, just forgot to switch them. Will update it, thanks

[giovannipizzi]

Thanks!
I'd be ready to approve, but maybe in the template can you please add another {} and say if the string originates from the stdout or the stderr?
Something like We detected some spurious output in {} ... and you set that to the string stderr or stdout accordingly

[sphuber]

@giovannipizzi done!