Update .travis.yml

Author: nygrenh

.travis.yml

@@ -21,7 +21,7 @@ before_install:
   - curl -L https://static.rust-lang.org/rustup.sh | sh -s -- --channel=stable --yes --prefix=$PWD --disable-sudo
   - export PATH=$PATH:$PWD/bin
   - export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$PWD/lib
-  - mkdir $HOME/bin && ln -s $(which python3.4) $HOME/bin/python3 && export PATH="$HOME/bin:$PATH"
+  - mkdir -p $HOME/bin && ln -s $(which python3.4) $HOME/bin/python3 && export PATH="$HOME/bin:$PATH"
   - mvn install -Dmaven.test.skip=true
 script:
   - mvn clean test