The warnings are triggered within package 'broom', not 'ggpmisc' package's code. The version of 'broom' currently in Github solves the problem. Be aware that DESCRIPTION has not been edited and consequently the updated version in Github has the same version number and date than that in CRAN, although it is different.
Pedro J. Aphaloreporter
Furthermore, the DESCRIPTION file in the unreleased version of 'broom' has not been updated to add 'purr' to the imports.