Quote line that contains a colon.

Author: mcflugen

.travis.yml

@@ -37,7 +37,7 @@ install:
 - conda info -a && conda list
 script:
 - mkdir -p $MPLCONFIGDIR
-- echo "backend: Agg" > $MPLCONFIGDIR/matplotlibrc
+- "echo backend: Agg > $MPLCONFIGDIR/matplotlibrc"
 - ./run-all-tests.sh
 virtualenv:
   system_site_packages: false