fix: variable name

Author: satra

.travis.yml

@@ -6,7 +6,7 @@ before_install:
     - sudo apt-get update -qq
     - sudo apt-get install lsb-release
     - source /etc/lsb-release
-    - wget -O- http://neuro.debian.net/lists/${$DISTRIB_CODENAME}.us-nh | sudo tee /etc/apt/sources.list.d/neurodebian.sources.list
+    - wget -O- http://neuro.debian.net/lists/${DISTRIB_CODENAME}.us-nh | sudo tee /etc/apt/sources.list.d/neurodebian.sources.list
     - sudo apt-key adv --recv-keys --keyserver pgp.mit.edu 2649A5A9
     - sudo apt-get update -qq
     - sudo apt-get install -qq python-scipy python-nose