CI: Always install latest pip version on recent Python 3 versions.

Tools/ci-run.sh

@@ -56,11 +56,15 @@ if [ -z "${PYTHON_VERSION##2.7}" ]; then
   pip install -r test-requirements-27.txt || exit 1
 elif [ -z "${PYTHON_VERSION##3.[45]*}" ]; then
   python -m pip install -r test-requirements-34.txt || exit 1
-elif [ -n "${PYTHON_VERSION##*-dev}" ]; then
-  python -m pip install -r test-requirements.txt || exit 1
+else
+  python -m pip install -U pip setuptools wheel || exit 1
+
+  if [ -n "${PYTHON_VERSION##*-dev}" ]; then
+    python -m pip install -r test-requirements.txt || exit 1
 
-  if [ "${PYTHON_VERSION##pypy*}" -a "${PYTHON_VERSION##3.[4789]*}" ]; then
-    python -m pip install -r test-requirements-cpython.txt || exit 1
+    if [ "${PYTHON_VERSION##pypy*}" -a "${PYTHON_VERSION##3.[4789]*}" ]; then
+      python -m pip install -r test-requirements-cpython.txt || exit 1
+    fi
   fi
 fi