Fix progress bar still capturing stderr after exception

[Neraste]

Fixes #15, fixes #22.

[codecov]

Codecov Report

Merging #16 into develop will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop      #16      +/-   ##
===========================================
+ Coverage    99.54%   99.54%   +<.01%     
===========================================
  Files            9        9              
  Lines          439      442       +3     
===========================================
+ Hits           437      440       +3     
  Misses           2        2

Impacted Files	Coverage Δ
src/dakara_base/progress_bar.py	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6de0760...93c7678. Read the comment docs.

[Nadeflore]

I remember this issue, so using a context manager should solve the problem.
Didn't test it, but it makes sense.

[Neraste]

I would like to open an issue on the progress bar repository.

[Neraste]

Looks like a similar issue was submitted, and that the progress bar can be already used as a context manager to prevent the problem. So this PR is redundant, but not the final use of the different progress bars. I will check that and adapt the code.

[Neraste]

I adapted the code, it is better to used the already provided secure mechanism.