merge more evolve stuff away (what?)

synthrepo: add missing import of sys Found using Cython.

transplant: pass source through to recover

repoview: remove more unreachable code Found using Cython.

merge away some failed evolve fat-fingering

pager: add missing imports of errno and shlex Found using Cython.

largefiles: quiet (and document) undefined name errors (issue3886) These names were found using Cython; I was completely puzzled until I searched the rest of the tree. It's icky to mess with another module's namespace, but ickier yet to do so without a comment :-)

color: add missing import of error Found using Cython.

pvec: use the correct name for an identifier Found using Cython.

repoview: remove unreachable code Found using Cython.