add ensure-autobahn.sh (dotnet#4)

BuildAgent/SetupScripts/Components/ensure-autobahn.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+
+set +e
+
+if ! type -p python >/dev/null 2>&1; then
+	echo "Requires python!" 1>&2
+	exit 1
+fi
+
+python -m ensurepip
+pip install virtualenv
+
+mkdir -p ~/virtualenvs
+
+if [ ! -d ~/virtualenvs/autobahntestsuite ]; then
+	virtualenv ~/virtualenvs/autobahntestsuite
+fi
+
+~/virtualenvs/autobahntestsuite/bin/pip install autobahntestsuite
+
+if [ -e /usr/local/bin/wstest ]; then
+	rm /usr/local/bin/wstest
+fi
+ln -s ~/virtualenvs/autobahntestsuite/bin/wstest /usr/local/bin/wstest