switch from open to io.open for text file read/write

[indirectlylit]

Summary

In learningequality/kolibri-installer-windows#72 we noticed that characters aren't being rendered properly in Windows using Python 3

This PR attempts to find all instances of open that were used on text files, and replace them with io.open, using an explicit encoding.

Reviewer guidance

Please check that this all makes sense

References

• 715c290
• e8d9aea
• Conditionally encode when reading stopword file #3743

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Contributor Checklist

• Contributor has fully tested the PR manually
• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If there are any front-end changes, before/after screenshots are included
• If this is an important user-facing change, PR or related issue has a 'changelog' label

Reviewer Checklist

• Automated test coverage is satisfactory
• Reviewer has fully tested the PR manually
• PR has been tested for accessibility regressions
• External dependencies files were updated (yarn and pip)
• Documentation is updated
• Link to diff of internal dependency change is included
• CHANGELOG.rst is updated for high-level changes
• Contributor is in AUTHORS.rst

[codecov]

Codecov Report

Merging #3769 into release-v0.10.x will decrease coverage by <.01%.
The diff coverage is 70.58%.

@@                 Coverage Diff                 @@
##           release-v0.10.x    #3769      +/-   ##
===================================================
- Coverage            76.74%   76.74%   -0.01%     
===================================================
  Files                  215      215              
  Lines                 8991     8999       +8     
  Branches              1110     1110              
===================================================
+ Hits                  6900     6906       +6     
- Misses                1856     1858       +2     
  Partials               235      235

Impacted Files	Coverage Δ
kolibri/utils/conf.py	84.21% <ø> (ø)	⬆️
kolibri/auth/management/commands/importusers.py	97.75% <ø> (ø)	⬆️
...bri/content/management/commands/generate_schema.py	0% <0%> (ø)	⬆️
...bri/logger/management/commands/generateuserdata.py	85.71% <100%> (+0.52%)	⬆️
kolibri/auth/constants/facility_presets.py	90% <100%> (+2.5%)	⬆️
kolibri/content/utils/stopwords.py	100% <100%> (ø)	⬆️
kolibri/content/hooks.py	77.14% <100%> (+0.67%)	⬆️
kolibri/core/webpack/hooks.py	66.48% <50%> (+0.17%)	⬆️

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[indirectlylit]

hmm looks like it's not building... checking on it

[mrpau-richard]

@indirectlylit the fix confirmed at the Windows 7. Non-english characters are now displaying properly.

[indirectlylit]

great!

might also help with #2541