bump CPython version

Author: timfel

ci.jsonnet

@@ -71,7 +71,7 @@
       "mercurial": ">=3.2.4",
       "gcc": "==4.9.1",
       "llvm": "==4.0.1",
-      "python": "==3.4.1",
+      "python": "==3.6.5",
       "libffi": ">=3.2.1",
       "bzip2": ">=1.0.6",
     },