Conda has slowly but surely gone down the drain as well. It used to be bullet proof but there too you now get absolutely unsolvable circular dependencies.
As for why conda: wheels do not have post-installation hooks (which given the issues with npm, I'm certainly a fan of), and while for most packages this isn't an issue, I've encountered enough packages where sadly they are required (for integration purposes), and the PyPI packages are subtlety broken on install without them. Additionally, conda (especially Anaconda Inc's commercial repositories) have significantly more optimised builds (not as good as the custom build well-run clusters provide, but better than PyPI-provided ones). I personally do not use conda (because I tend to want to test/modify/patch/upstream packages lower down the chain and test with higher up packages), but for novices (especially novices on Windows), conda for all its faults is the best option for those in the "data science" ecosystem.
Probably either one of python-serial python-pexpect judging by the file dates, and neither of these are so exciting that there should have been any version conflicts at all.
And the only reason I had to rebuild it at all was due to another version conflict in the apm distribution that expects a particular version of pixbuf to be present on the system and all hell breaks loose if it isn't, and you can't install that version on a modern system because that breaks other packages.
It is insane how bad all this package management crap is. The GNU project and the linux kernel are the only ones that have never given me any trouble.