fix: flush output even on fail

[18alantom]

Fixes a few issues in: #1631

[codecov]

Codecov Report

Attention: Patch coverage is 69.44444% with 22 lines in your changes are missing coverage. Please review.

Project coverage is 39.20%. Comparing base (2624123) to head (1539785).
Report is 11 commits behind head on master.

❗ Current head 1539785 differs from pull request most recent head 73c1e02. Consider uploading reports for the commit 73c1e02 to get more accurate results

Files	Patch %	Lines
...press/doctype/deploy_candidate/deploy_candidate.py	62.06%	11 Missing ⚠️
.../doctype/deploy_candidate/docker_output_parsers.py	68.57%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1665      +/-   ##
==========================================
+ Coverage   38.72%   39.20%   +0.48%     
==========================================
  Files         317      317              
  Lines       25371    25407      +36     
==========================================
+ Hits         9824     9960     +136     
+ Misses      15547    15447     -100     

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