Make possible to start without a details.json file

Signed-off-by: Mattia Rizzolo <mattia@debian.org>

managetests/utils.py

@@ -58,10 +58,17 @@ def is_root_valid(path):
         print('There is a branches file conflicting with the expected directory')
         return False
 
-# TODO make possible to start without these two files
-    required_files = ["config.json", "details.json"]
-    for file in required_files:
-        file = path / file
+    # details.json file
+    file = path / 'details.json'
+    if not file.exists():
+        with open(file, 'w') as f:
+            f.write('{"branches":{}}')
+    elif not file.is_file():
+        print('There is a details.json non-file conflicting with the expectations.')
+        return False
+
+    # TODO make possible to start without this file
+    file = path / 'config.json'
     if not (file.exists() and file.is_file()):
         print("The required file %s does not exist" % file)
         return False