wrap url parsing exceptions from urllib3's PoolManager

[nateprewitt]

This should address #4746 by catching and wrapping all LocationValueErrors and rewrapping them under the Requests namespace as InvalidURL.

[codecov-io]

Codecov Report

Merging #4765 into master will increase coverage by 0.02%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           master    #4765      +/-   ##
==========================================
+ Coverage   66.77%   66.79%   +0.02%     
==========================================
  Files          15       15              
  Lines        1568     1572       +4     
==========================================
+ Hits         1047     1050       +3     
- Misses        521      522       +1

Impacted Files	Coverage Δ
requests/adapters.py	70.27% <80%> (+0.08%)	⬆️

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