Use Jinja templating syntax.

playbooks/roles/common/tasks/create_venv.yml

@@ -22,13 +22,13 @@
   - install
 
 - name: create edx virtualenv directory
-  file: path=$venv_dir owner=ubuntu group=adm mode=2775 state=directory
+  file: path={{ venv_dir }} owner=ubuntu group=adm mode=2775 state=directory
   tags:
   - venv_base
   - install
 
 - name: create the edx virtualenv directory initial contents
-  command: /usr/local/bin/virtualenv $venv_dir --distribute creates=$venv_dir/bin/activate
+  command: /usr/local/bin/virtualenv {{ venv_dir }} --distribute creates=$venv_dir/bin/activate
   tags:
   - venv_base
   - install