Fix bash limitation (https://github.com/pypa/virtualenv/issues/596)

Change-Id: Ia25697f341ceed67b5609d4d155292dab955378e
diff --git a/tests/run_tests.sh b/tests/run_tests.sh
index cf3dfa7..3d1f1a1 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -46,10 +46,10 @@
     dependency_check virtualenv
     virtualenv $VENV_DIR
     source ${VENV_DIR}/bin/activate
-    pip install salt${PIP_SALT_VERSION}
-    pip install jsonschema
+    python $(which pip) install salt${PIP_SALT_VERSION}
+    python $(which pip) install jsonschema
     if [[ -f ${CURDIR}/pip_requirements.txt ]]; then
-       pip install -r ${CURDIR}/pip_requirements.txt
+       python $(which pip) install -r ${CURDIR}/pip_requirements.txt
     fi
 }
 
@@ -167,7 +167,7 @@
 lint_releasenotes() {
     [[ ! -f "${VENV_DIR}/bin/activate" ]] && setup_virtualenv
     source ${VENV_DIR}/bin/activate
-    pip install reno
+    python $(which pip) install reno
     reno lint ${CURDIR}/../
 }