Move pycobertura installation into a pre-run

Change-Id: I850b17473f8532e09b6ece4d8f8debb490f7ff59
diff --git a/roles/ensure-pycobertura/tasks/main.yaml b/roles/ensure-pycobertura/tasks/main.yaml
new file mode 100644
index 0000000..473d543
--- /dev/null
+++ b/roles/ensure-pycobertura/tasks/main.yaml
@@ -0,0 +1,4 @@
+- name: Ensure pycobertura is available
+  pip:
+    name: pycobertura
+    extra_args: --user