Handle errors from coveralls more gracefully.

Since we have moved coveralls to the script target the entire build will
now fail if coveralls fail. We handle it more gracefully by echo'ing the
failure instead of doing a hard-failure.

See: https://bugs.torproject.org/29036

.travis.yml

@@ -156,7 +156,7 @@ script:
   - if [[ "$DISTCHECK" == "" ]]; then make check; fi
   - if [[ "$DISTCHECK" != "" ]]; then make distcheck DISTCHECK_CONFIGURE_FLAGS="$CONFIGURE_FLAGS"; fi
   ## If this build was one that produced coverage, upload it.
-  - if [[ "$COVERAGE_OPTIONS" != "" ]]; then coveralls -b . --exclude src/test --exclude src/trunnel --gcov-options '\-p'; fi
+  - if [[ "$COVERAGE_OPTIONS" != "" ]]; then coveralls -b . --exclude src/test --exclude src/trunnel --gcov-options '\-p' || echo "Coverage failed"; fi
 
 after_failure:
   ## configure will leave a log file with more details of config failures.