Pin xandikos to 0.1.0

Author: Hugo Osvaldo Barrera

tests/storage/servers/xandikos/install.sh

@@ -4,7 +4,8 @@ set -e
 pip install wsgi_intercept
 
 if [ "$REQUIREMENTS" = "release" ] || [ "$REQUIREMENTS" = "minimal" ]; then
-    pip install -U xandikos
+    # XXX: This is the last version to support Python 3.5
+    pip install -U "xandikos==0.1.0"
 elif [ "$REQUIREMENTS" = "devel" ]; then
     pip install -U git+https://github.com/jelmer/xandikos
 else