  It was suggested that observations of the solar system exclude massive
gravity, in the sense that the graviton mass must be rigorously zero. This is
because there is a discontinuity in the linearized gravity theory at graviton
mass equal to zero. The linearized Schwarzschild metric is not recovered for
infinitesimal graviton mass, contradicting observations on light deviation by
the Sun and Mercury perihelion advance. It was then argued that
non-perturbative effects make the massive gravity theory continuous in the
graviton mass. Both the original suggestion and its refutation were based on a
non-covariant and linearized action, and the physical interpretation of these
results remained questionable. Here we use a covariant quasi-massive gravity
theory that is known to be discontinuous in the graviton mass in the linear
approximation. We show that non-perturbative effects do restore the continuity;
the weak-field Schwarzschild solution is recovered in the limit of small
graviton mass. We also show that weak-field Schwarzschild with matter is
recovered for infinitesimal graviton mass. Thus: Observations of the solar
system only put an upper limit on the graviton mass (in the context of the
gravity theory that we use, inverse graviton mass, as measured at distances of
order inverse graviton mass, is $\gtrsim 100$ Mpc). But graviton can be
massive, with a cosmologically interesting mass.
