Is it possible to re-check the dependencies of packages installed with pip? That is, suppose we have a working environment. Then, one of the packages changes (gets upgraded, etc). Is there a command one can run to make to make sure that the dependency tree is still sound and does not have conflicts?
Nowadays python -m pip check should do the trick.
Seems to have been added as early as pip 9.0.0 released on 2016-11-02.
It's not part of pip, but there is a tool you can use called pip-conflict-checker. Just install it through pip and run pipconflictchecker to get a dump of all the conflicts. pipdeptree could also help here.
You might also be interested in reading this article about dealing with pip dependency issues. The article also discusses the two tools I mentioned above along with strategies to fix broken dependencies.
In recent pip versions using pip install -r requirements.txt will fail if you have any conflict in your dependencies specified in requirements.txt.