self._propagate_incompatibility will return the _conflict type which is the hashable type used to represent a package (in my usecase this is not a string). The line converts it to str which is a problem since then it is no longer a valid key in the self._incompatibilities dictionary (line 113 of the same function).
I believe it's this line:
https://github.com/sdispater/mixology/blob/067c5aef14d7caeb733adff2b34e9489797f5113/mixology/version_solver.py#L130
self._propagate_incompatibilitywill return the _conflict type which is the hashable type used to represent a package (in my usecase this is not a string). The line converts it to str which is a problem since then it is no longer a valid key in theself._incompatibilitiesdictionary (line 113 of the same function).https://github.com/sdispater/mixology/blob/067c5aef14d7caeb733adff2b34e9489797f5113/mixology/version_solver.py#L98-L133