Improve error messages from C parser (#7366)

[Dreamsorcerer]

(cherry picked from commit 1a48add)

[codecov]

Codecov Report

Merging #7380 (2d0c251) into 3.8 (9337fb3) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##              3.8    #7380   +/-   ##
=======================================
  Coverage   97.38%   97.38%           
=======================================
  Files         107      107           
  Lines       31000    31012   +12     
  Branches     3926     3928    +2     
=======================================
+ Hits        30190    30202   +12     
  Misses        605      605           
  Partials      205      205           

Flag	Coverage Δ
CI-GHA	97.25% <100.00%> (+<0.01%)	⬆️
OS-Linux	96.89% <100.00%> (-0.01%)	⬇️
OS-Windows	95.22% <100.00%> (+<0.01%)	⬆️
OS-macOS	96.64% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	94.82% <100.00%> (-0.01%)	⬇️
Py-3.10.12	96.48% <100.00%> (+<0.01%)	⬆️
Py-3.11.0	96.19% <81.48%> (-0.02%)	⬇️
Py-3.6.15	96.37% <100.00%> (+<0.01%)	⬆️
Py-3.6.8	94.75% <100.00%> (+<0.01%)	⬆️
Py-3.7.17	96.52% <100.00%> (+<0.01%)	⬆️
Py-3.7.9	94.88% <100.00%> (+<0.01%)	⬆️
Py-3.8.10	94.80% <100.00%> (+<0.01%)	⬆️
Py-3.8.17	96.43% <100.00%> (-0.06%)	⬇️
Py-3.9.13	94.80% <100.00%> (-0.01%)	⬇️
Py-3.9.17	96.45% <100.00%> (-0.01%)	⬇️
Py-pypy7.3.11	93.91% <77.77%> (-0.03%)	⬇️
VM-macos-latest	96.64% <100.00%> (+<0.01%)	⬆️
VM-ubuntu-20.04	96.83% <100.00%> (-0.05%)	⬇️
VM-ubuntu-latest	96.41% <81.48%> (-0.02%)	⬇️
VM-windows-latest	95.22% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
aiohttp/http_exceptions.py	100.00% <100.00%> (ø)
tests/test_http_exceptions.py	100.00% <100.00%> (ø)
tests/test_http_parser.py	99.08% <100.00%> (+<0.01%)	⬆️

... and 3 files with indirect coverage changes

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