knitty installation overwrites user-owned executables in (e.g.) ~/.local/bin

[phlummox]

From experimentation, it seems as if knitty tries (via py-pandoc) to install a Pandoc executable in ~/.local/bin, even if a recent Pandoc (e.g. 2.17.1.1) is on the PATH; and it overwrites any executable which might already exist at ~/.local/bin/pandoc.

That doesn't seem very friendly, nor expected, behaviour for a Python package. The user might already have a version of Pandoc sitting in ~/.local/bin that they're quite attached to. knitty shouldn't be removing or overwriting programs the user has already installed. If knitty wants a known version of Pandoc installed in a place it has control over, I'd imagine the appropriate spot is in site-packages/knitty.