Add quotes to env command

.travis.yml

@@ -14,12 +14,12 @@ cache:
     - downloads
 
 env:
-  - DOCKER_DOWNGRADE=echo nothing to be done
-  - DOCKER_DOWNGRADE=sudo apt-get autoremove -y docker-ce &
+  - DOCKER_DOWNGRADE=\"echo nothing to be done\"
+  - DOCKER_DOWNGRADE=\"sudo apt-get autoremove -y docker-ce &
     curl -fsSL https://apt.dockerproject.org/gpg | sudo apt-key add - &
     sudo apt-add-repository "deb https://apt.dockerproject.org/repo ubuntu-$(lsb_release -cs) main" &
     sudo apt-get update &
-    sudo apt-get install docker-engine=1.12.6-0~ubuntu-$(lsb_release -cs)
+    sudo apt-get install docker-engine=1.12.6-0~ubuntu-$(lsb_release -cs)\"
 
 before_install:
   - curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
@@ -38,7 +38,7 @@ script:
   - make vet
   - make build-devserver
   - make build-devjmstest
-  - exec $DOCKER_DOWNGRADE
+  - $DOCKER_DOWNGRADE
   - make test-devserver
 
 after_success: