  We predict the existence of non-Hermitian topologically protected end states
in a one-dimensional exciton-polariton condensate lattice, where topological
transitions are driven by the laser pump pattern. We show that the number of
end states can be described by a Chern number and a topological invariant based
on the Wilson loop. We find that such transitions arise due to {\it enforced
exceptional points} which can be predicted directly from the bulk Bloch wave
functions. This allows us to establish a new type of bulk-boundary
correspondence for non-Hermitian systems and to compute the phase diagram of an
open chain analytically. Finally, we demonstrate topological lasing of a single
end-mode in a realistic model of a microcavity lattice.
