Don't use urljoin for prepending a forward slash to paths.

[lewiscollard]

Fixes #273.

Previously, Path used urljoin to prepend a forward slash to the path. But urljoin, for no good reason I can see, breaks if you have two slashes in a path:

>>> from urllib.parse import urljoin
>>> urljoin("/", "oh//no")
'/oh/no'

This manifests itself as respx asserting that routes were not called if they contained two forward slashes in the path part. Fix this by just adding a "/" if it's not there, which is what this was trying to do in the first place.

[sparrowt]

This looks good to me, any thoughts @lundberg?

[lundberg]

Looks good! Thanks @lewiscollard

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (b3d8e9d) to head (dfd38b4).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #302   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           22        22           
  Lines         2933      2934    +1     
  Branches       199       200    +1     
=========================================
+ Hits          2933      2934    +1     

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[sparrowt]

Thanks @lundberg! Would there be any chance of a new release please? Though I fully appreciate life can be busy.
0.22.0...master

We have a test that fails intermittently when there are 2 sequential slashes in a base64 value that ends up in the URL (don't ask...!)