Fixes #18178: Unparsable techniques when there are error in cf-promises (cf-promises outputs error in stdout)

[VinceMacBuche]

https://issues.rudder.io/issues/18178

[Normation-Quality-Assistant]

This PR breaks qa-test

-- stdout -- 
Branch 'branches/rudder/6.1' set up to track remote branch 'branches/rudder/6.1' from 'NRM'.
Your branch is up to date with 'NRM/branches/rudder/6.1'.
Already up to date.
Already up to date.
[...]
  File "/var/lib/jenkins/jobs/merge-accepted-pr/workspace/repos/ncf/tools/ncf.py", line 83, in check_output
    if line.startsWith("{"):
AttributeError: 'unicode' object has no attribute 'startsWith'

----------------------------------------------------------------------
Ran 16 tests in 1.736s

FAILED (errors=16)
make: *** [Makefile:53: test-common] Error 1

You should run ./qa-test in your repository to make sure it works.
You can also run rudder-dev merge https://github.com/Normation/ncf/pull/1240 --test to test with upmerging.
After this, you can remove the qa: Can't merge ta
-- Your faithful QA (https://ci.normation.com/jenkins/job/merge-accepted-pr/29776/console)

[amousset]

python 💥

[amousset]

what an enfer

[VinceMacBuche]

PR updated with a new commit

[Normation-Quality-Assistant]

This PR breaks qa-test

-- stdout -- 
Branch 'branches/rudder/6.1' set up to track remote branch 'branches/rudder/6.1' from 'NRM'.
Your branch is up to date with 'NRM/branches/rudder/6.1'.
Already up to date.
Your branch is up to date with 'NRM/branches/rudder/6.1'.
[...]
  File "/var/lib/jenkins/jobs/merge-accepted-pr/workspace/repos/ncf/tools/ncf.py", line 332, in parse_technique_methods
    raise NcfError("An error occured while parsing technique '"+technique_file+"'", cause = e)
NcfError: "An error occured while parsing technique '/var/lib/jenkins/jobs/merge-accepted-pr/workspace/repos/ncf/tests/unit/test_technique.cf'"

----------------------------------------------------------------------
Ran 16 tests in 1.802s

FAILED (errors=16)
make: *** [Makefile:53: test-common] Error 1

You should run ./qa-test in your repository to make sure it works.
You can also run rudder-dev merge https://github.com/Normation/ncf/pull/1240 --test to test with upmerging.
After this, you can remove the qa: Can't merge ta
-- Your faithful QA (https://ci.normation.com/jenkins/job/merge-accepted-pr/29779/console)

[VinceMacBuche]

Everything is good python,

Mutable variable, enumerate through index, break in loop, and wonderful splice syntax

python/20

[VinceMacBuche]

PR updated with a new commit

[Normation-Quality-Assistant]

OK, squash merging this PR