fix check issue

src/source_localization/obs.py

@@ -181,9 +181,10 @@ class Obs:
         for i in range(1, self.nb_dt_in_obs_time_window):
             if (self.index_obs_to_index_time_est[:, i - 1] <= 0).any():
                 raise ValueError(
-                    "The time window of integration of the observation operator for the first observation starts before the temporal domain."
+                    "The time window of integration of the observation operator for the first observation"
+                    + " starts before the temporal domain."
                     + " This is probably because the integration time window is too large or the observation times are inaccurate."
-                    )
+                )
             self.index_obs_to_index_time_est[:, i] = self.index_obs_to_index_time_est[:, i - 1] - 1
 
         # initialization of the dictionnary containing the indexes of the observations given the time index