fix error in travis

Author: Oscar Esteban

.travis.yml

@@ -19,7 +19,7 @@ before_install:
 - if $INSTALL_DEB_DEPENDECIES; then sudo ln -s /run/shm /dev/shm; fi
 # Enable universe and multiverse
 - sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu/ trusty main universe multiverse"
-- sudo add-apt-repository "deb-src http://archive.ubuntu.com/ubuntu trusty main universe multiverse"
+- sudo add-apt-repository "deb-src http://archive.ubuntu.com/ubuntu trusty universe multiverse"
 - bash <(wget -q -O- http://neuro.debian.net/_files/neurodebian-travis.sh)
 - sudo apt-get update
 # Fix numpy problem: https://github.com/enthought/enable/issues/34#issuecomment-2029381