message from `sessioninfo::python_info()`

[tyner]

One may use the RETICULATE_PYTHON environment to tell reticulate where to look for python. And in fact sessioninfo::python_info() (and hence sessioninfo::session_info(info = "python")) are quite aware of this (by calling reticulate::py_config()) , but only if isNamespaceLoaded("reticulate") && reticulate::py_available(initialize = FALSE) is already TRUE.

Perhaps that is desirable (because we don't want sessioninfo::python_info() to have side-effects), but maybe instead of saying "Python is not available" perhaps sessioninfo::python_info() could say "Python is not available (or reticulate::py_config has not been called yet)" ?