  We present robust planet occurrence rates for Kepler planet candidates around
M stars for planet radii $R_p = 0.5-4~\textrm{R}_\oplus$ and orbital periods $P
= 0.5-256$ days using the approximate Bayesian computation (ABC) technique.
This work incorporates the final Kepler DR25 planet candidate catalog and data
products and augments them with updated stellar properties using Gaia DR2 and
2MASS PSC. We apply a set of selection criteria to select a sample of 1,746
Kepler M dwarf targets that host 89 associated planet candidates. These early M
dwarfs and late K dwarfs were selected from cross-referenced targets using
several photometric quality flags from Gaia DR2 and color-magnitude cuts using
2MASS magnitudes. We estimate a habitable zone occurrence rate of
$f_{\textrm{M,HZ}} = 0.33^{+0.10}_{-0.12}$ for planets with $0.75-1.5$
R$_\oplus$ size. We caution that occurrence rate estimates for Kepler M stars
are sensitive to the choice of prior due to the small sample of target stars
and planet candidates. For example, we find an occurrence rate of
$4.2^{+0.6}_{-0.6}$ or $8.4^{+1.2}_{-1.1}$ planets per M dwarf (integrating
over $R_p = 0.5-4~\textrm{R}_\oplus$ and $P = 0.5-256$ days) for our two
choices of prior. These occurrence rates are greater than those for FGK dwarf
target when compared at the same range of orbital periods, but similar to
occurrence rates when computed as a function of equivalent stellar insolation.
Combining our result with recent studies of exoplanet architectures indicates
that most, and potentially all, early-M dwarfs harbor planetary systems.
