Fix bobrc json format

bob/devtools/data/bobrc

 {
-    "bob_data_folder": "./bob_data",
+    "bob_data_folder": "./bob_data"
 }

bob/devtools/test_ci.py

 #!/usr/bin/env python
 # coding=utf-8
+import json
 
 from .ci import is_private
+from .constants import BOBRC_PATH
 
 
 def test_is_private():
@@ -9,3 +11,9 @@ def test_is_private():
     base_url = "https://gitlab.idiap.ch"
     assert not is_private(base_url, "bob/bob.extension")
     assert is_private(base_url, "bob/private")
+
+
+def test_bobrc_json_validity():
+
+    with open(BOBRC_PATH) as f:
+        json.load(f)