Generate xml report coverage

Author: wvangeit

.codeclimate.yml

@@ -36,8 +36,8 @@ commands =
     style: pycodestyle --ignore=E402,W503,W504 bluepyopt
     syntax: flake8 . --count --select=E9,F63,F72,F82 --show-source --statistics
 
-    unit: pytest --cov=bluepyopt --cov-append bluepyopt/tests -k unit
-    functional: pytest --cov=bluepyopt --cov-append bluepyopt/tests -k-unit
+    unit: pytest --cov=bluepyopt --cov-append --cov-report=xml bluepyopt/tests -k unit
+    functional: pytest --cov=bluepyopt --cov-append --cov-report=xml bluepyopt/tests -k-unit
 
 [testenv:docs]
 basepython = python3.6