Fixed #1129: render all widget attributes for file fields in bootsrap4

[anneFly]

I've explained the issue a bit more in #1129 .
The main change is that the template now uses widget.data.attrs and that widget.data.attrs.class is explicitly rendered when it's there. Please let me know if you need more/different test coverage or different naming.

[codecov-io]

Codecov Report

Merging #1130 (86ee486) into master (56a423e) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1130      +/-   ##
==========================================
+ Coverage   97.23%   97.24%   +0.01%     
==========================================
  Files          23       23              
  Lines        2816     2829      +13     
  Branches      243      243              
==========================================
+ Hits         2738     2751      +13     
  Misses         38       38              
  Partials       40       40              

Flag	Coverage Δ
unittests	97.20% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
crispy_forms/tests/forms.py	100.00% <100.00%> (ø)
crispy_forms/tests/test_layout.py	99.72% <100.00%> (+<0.01%)	⬆️

---

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 56a423e...86ee486. Read the comment docs.

[smithdc1]

Hi Anne -- Thanks for this, it looks good to me.

The tests don't seem to be running, I've tried to restart them but it seems a bit stuck 🕵️ -- https://github.com/django-crispy-forms/django-crispy-forms/actions/runs/655500429

If it's still not completed in the morning, could you try rebasing to see if that spurs it into life?

[anneFly]

@smithdc1 looks like the tests have been running by now. All green :)

[smithdc1]

@anneFly that's good news. Thanks again for the contribution!