I cannot find any documents on what to use our current pex::exceptions for. Many of them are similar to the std::c++ exceptions, but even having links to the "matching" C++ doc for each exception would be a start. Some of our exceptions have no std:: counterpart. Either way, it's often unclear at the C++ layer what one should raise. Even a single sentence each would be a good start.
If this documentation does exist, I can't readily find it in our doxygen or source code.
Adding a large watcher list, since when I brought this up on slack, Jim Bosch said
...first someone has to actually decide what those uses are, and the list of people who feel empowered to decide that is very small.