[CI] Fix coverage job

Changes:
  * start using pytest-cov library
  * if there are uncommitted changes then do not try to
    stash them automatically but exit with error message

Co-Authored-By: Andrey Kurilin <andr.kurilin@gmail.com>
Co-Authored-By: Alexander Maretskiy <amaretskiy@mirantis.com>

Change-Id: Id5f396550a600fe0ab899b09aceff60b3d98dc0e

.coveragerc

@@ -6,3 +6,6 @@ source = rally
 ignore_errors = True
 precision = 3
 omit = */migrations/versions/ca3626f62937_init_migration.py
+
+[html]
+directory = cover

test-requirements.txt

@@ -3,6 +3,7 @@
 # process, which may cause wedges in the gate later.
 hacking<0.10,>=0.9.2
 pytest>=2.7
+pytest-cov>=2.2.1
 pytest-html
 
 coverage>=3.6 # Apache-2.0

tests/ci/cover.sh

@@ -22,24 +22,28 @@ show_diff () {
     diff -U 0 $1 $2 | sed 1,2d
 }
 
-# Stash uncommitted changes, checkout master and save coverage report
-uncommited=$(git status --porcelain | grep -v "^??")
-[[ -n $uncommited ]] && git stash > /dev/null
+if ! git diff --exit-code || ! git diff --cached --exit-code
+then
+    echo "There are uncommited changes!"
+    echo "Please clean git working directory and try again"
+    exit 1
+fi
+
+# Checkout master and save coverage report
 git checkout HEAD^
 
 baseline_report=$(mktemp -t rally_coverageXXXXXXX)
-find . -type f -name "*.pyc" -delete && python setup.py testr --coverage --testr-args="$*"
+py.test --cov=rally tests/unit/ --cov-report=html
 coverage report > $baseline_report
+mv cover cover-master
 cat $baseline_report
 baseline_missing=$(awk 'END { print $3 }' $baseline_report)
 
-# Checkout back and unstash uncommitted changes (if any)
+# Checkout back and save coverage report
 git checkout -
-[[ -n $uncommited ]] && git stash pop > /dev/null
 
-# Generate and save coverage report
 current_report=$(mktemp -t rally_coverageXXXXXXX)
-find . -type f -name "*.pyc" -delete && python setup.py testr --coverage --testr-args="$*"
+py.test --cov=rally tests/unit/ --cov-report=html
 coverage report > $current_report
 current_missing=$(awk 'END { print $3 }' $current_report)