Don't use ansible module to install xqwatcher requirements.

There is a bug in the pip module in the current version of ansible that makes it not
work with python3 virtualenvs.  The bug is fixed in ansible 2.3.2.

playbooks/roles/xqwatcher/tasks/code_jail.yml

@@ -85,11 +85,7 @@
     - install:code
 
 - name: Install course specific python requirements
-  pip:
-    requirements: "{{ xqwatcher_app_data }}/{{ item.QUEUE_CONFIG.HANDLERS[0].CODEJAIL.name }}-requirements.txt"
-    virtualenv: "{{ xqwatcher_app_dir }}/venvs/{{ item.QUEUE_CONFIG.HANDLERS[0].CODEJAIL.name }}"
-    state: present
-    extra_args: "{{ XQWATCHER_PIP_EXTRA_ARGS }}"
+  shell: "{{ xqwatcher_app_dir }}/venvs/{{ item.QUEUE_CONFIG.HANDLERS[0].CODEJAIL.name }}/bin/pip install {{ XQWATCHER_PIP_EXTRA_ARGS }} -r {{ xqwatcher_app_data }}/{{ item.QUEUE_CONFIG.HANDLERS[0].CODEJAIL.name }}-requirements.txt"
   with_items: "{{ XQWATCHER_COURSES }}"
   tags:
     - install