Handle case when headers argument of ResponseStream constructor is None

[liamcoatman]

The default value for the headers argument is None. This leads to an Exception when headers is passed to the Header constructor, which is expecting a Mapping type.

[codecov]

Codecov Report

Patch coverage: 66.666% and project coverage change: -0.098 ⚠️

Comparison is base (c21999a) 88.981% compared to head (6a47eb0) 88.884%.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #2729       +/-   ##
=============================================
- Coverage   88.981%   88.884%   -0.098%     
=============================================
  Files           92        92               
  Lines         6979      6981        +2     
  Branches      1190      1191        +1     
=============================================
- Hits          6210      6205        -5     
- Misses         527       531        +4     
- Partials       242       245        +3     

Impacted Files	Coverage Δ
sanic/response/types.py	85.082% <66.666%> (+0.166%)	⬆️

... and 2 files with indirect coverage changes

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[ahopkins]

Can you add some unit tests?

[liamcoatman]

@ahopkins I've added a test, which was failing prior to my fix and is now passing. I've probably put it in the wrong place, so let me know if you want me to move it.

[ahopkins]

It's a long file, but I'd dump it here: https://github.com/sanic-org/sanic/blob/main/tests/test_response.py

[liamcoatman]

In case you missed it, I moved the test to test_response.py as suggested

[QylinFly]

ResponseStream is not stream,bug?

[ahopkins]

ResponseStream is not stream,bug?

Sorry, I don't understand your question.