fix for python3

scenariosAleatoires/MCMC_class.py

@@ -311,7 +311,7 @@ class Scenario :
 		with gzip.GzipFile('./initial_scenario_indices.gz','w') as fid_gz:
 
 			json_str = json.dumps(dict_indices, ensure_ascii=False)
-			fid_gz.write(json_str)
+			fid_gz.write(json_str.encode('utf-8'))
 
 	'''
 	These functions returns values of indices of this scenario