Fix packages output parsing problem

Author: jcollins-g

tool/travis.sh

@@ -34,7 +34,7 @@ elif [ "$DARTDOC_BOT" = "packages" ]; then
   fi
   PACKAGE_NAME=access PACKAGE_VERSION=">=1.0.1+2" pub run grinder build-pub-package
   # Negative test for flutter_plugin_tools, make sure right error message is displayed.
-  PACKAGE_NAME=flutter_plugin_tools PACKAGE_VERSION=">=0.0.14+1" pub run grinder build-pub-package 2>&1 | grep "Generation failed: dartdoc could not find any libraries to document.$"
+  PACKAGE_NAME=flutter_plugin_tools PACKAGE_VERSION=">=0.0.14+1" pub run grinder build-pub-package 2>&1 | grep "dartdoc failed: dartdoc could not find any libraries to document.$"
   PACKAGE_NAME=shelf_exception_handler PACKAGE_VERSION=">=0.2.0" pub run grinder build-pub-package
 elif [ "$DARTDOC_BOT" = "sdk-analyzer" ]; then
   echo "Running main dartdoc bot against the SDK analyzer"