Dijkstra convergence error

[gecoombs]

Date: 18/07/23 Version Number: 0.2.15 -> 0.2.16

Description of change

This PR fixes an issue where if the Dijsktra route construction reached a point where it could not converge it simply exited with an exception. It now sets the cost of visiting that point to infinity and tries alternative paths.

Fixes #211

Testing

• [x] My changes result in all required regression tests passing without the need to update test files.

Files changed: polar_route/crossing.py

Test dump: pytest_dump.txt

Checklist

• [x] My code follows pep8 style guidelines.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [x] I have updated the documentation of the codebase where required.
• [x] My changes generate no new warnings.
• [x] My PR has been made to the 0.2.x branch (DO NOT SUBMIT A PR TO MAIN)