Change LOG(ERROR) to LOG(WARNING) in schur_complement_solver.cc

Change-Id: Ie248989b230ec2357a00a15ef35087e85682315c

internal/ceres/schur_complement_solver.cc

diff --git a/internal/ceres/schur_complement_solver.cc b/internal/ceres/schur_complement_solver.cc
index 54f00dd..9b7d4e5 100644
--- a/internal/ceres/schur_complement_solver.cc
+++ b/internal/ceres/schur_complement_solver.cc
@@ -318,7 +318,7 @@
   cholmod_rhs = NULL;
 
   if (cholmod_solution == NULL) {
-    LOG(ERROR) << "CHOLMOD solve failed.";
+    LOG(WARNING) << "CHOLMOD solve failed.";
     return false;
   }