Cherry pick PRs to backport to 19.12LTS

[ashleysommer]

Includes fixes from:
#1762
#1764
#1789

[ashleysommer]

Travis Type Checks are failing because 19.12LTS branch was never expected to have that level of type checking on it. The failures are not related to the commits in this PR.

[ahopkins]

@sjsadowski Let's try and circle back up on this early next week to get this built and pushed.

[ahopkins]

#1779?

[ashleysommer]

Oh, I didn't know #1779 exists. Though it looks like a rollup up a lot more commits between end of December 2019 and February 2020. I'll comment in that PR.

[ashleysommer]

Double checking everything on this, tests look fine (just a couple of mypy fails in asgi.py unrelated to these changes).

[codecov]

Codecov Report

Merging #1849 into 19.12LTS will decrease coverage by 2.81%.
The diff coverage is 57.14%.

@@             Coverage Diff              @@
##           19.12LTS    #1849      +/-   ##
============================================
- Coverage     92.30%   89.48%   -2.82%     
============================================
  Files            22       25       +3     
  Lines          2274     2930     +656     
  Branches        419      543     +124     
============================================
+ Hits           2099     2622     +523     
- Misses          135      235     +100     
- Partials         40       73      +33     

Impacted Files	Coverage Δ
sanic/server.py	74.15% <16.66%> (ø)
sanic/app.py	91.91% <84.61%> (-0.35%)	⬇️
sanic/response.py	100.00% <100.00%> (ø)
sanic/worker.py	82.64% <0.00%> (-0.15%)	⬇️
sanic/router.py	95.49% <0.00%> (-0.07%)	⬇️
sanic/request.py	99.60% <0.00%> (-0.03%)	⬇️
sanic/testing.py	97.91% <0.00%> (-0.03%)	⬇️
sanic/views.py	100.00% <0.00%> (ø)
... and 5 more

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[ahopkins]

@ashleysommer GitHub was complaining and would not let me push to your branch. So I created a new branch here and a new PR: #1900.