Fix where singularity build ends up with empty parameter

[pvanheus]

The current code yields this command:

ERROR    Command '['singularity', 'build', '',                                           utils.py:57
                             '[PATH]/quay.io-biocontainers-csvtk-0.31.0--h9ee0642_0.img'
                             , 'docker://quay.io/biocontainers/csvtk:0.31.0--h9ee0642_0']' returned non-zero
                             exit status 1.

This PR does two things:

1. It uses shlex.split rather than string.split to avoid the above-mentioned problem
2. It produces output event if the command fails (current code raises an exception before producing output)

[rpetit3]

TYVM @pvanheus

Similar lint/format test fail, I'll fix on my end