  We use the largest sample to date of spectroscopic SN Ia distances and
redshifts to look for evidence in the Hubble diagram of large scale outflows
caused by local voids suggested to exist at z<0.15. Our sample combines data
from the Pantheon sample with the Foundation survey and the most recent release
of lightcurves from the Carnegie Supernova Project to create a sample of 1295
SNe over a redshift range of 0.01<z<2.26. We make use of an inhomogeneous and
isotropic Lemaitre-Tolman-Bondi metric to model a void in the SN Ia
distance-redshift relation. We conclude that the SN luminosity
distance-redshift relation is inconsistent at the 4-5 sigma confidence level
with large local underdensities (|delta| > 20%, where the density contrast
delta = Delta rho /rho) proposed in some galaxy count studies, and find no
evidence of a change in the Hubble constant corresponding to a void with a
sharp edge in the redshift range 0.023<z<0.15. With empirical precision of
sigma_H_0 = 0.60%, we conclude that the distance ladder measurement is not
affected by local density contrasts, in agreement with cosmic variance of
sigma_H_0 = 0.42% predicted from simulations of large-scale structure. Given
that uncertainty in the distance ladder value is sigma_H_0=2.2%, this does not
affect the Hubble tension. We derive a 5 sigma constraint on local density
contrasts on scales larger than 69 megaparsec h^-1 of delta < 27%. The presence
of local structure does not appear to impede the possibility of measuring the
Hubble constant to 1% precision.
