changed two exceptions slightly to preserve original traceback

tsam/timeseriesaggregation.py

@@ -387,21 +387,21 @@ def _check_init_args(self):
             try:
                 timedelta = self.timeSeries.index[1] - self.timeSeries.index[0]
                 self.resolution = float(timedelta.total_seconds()) / 3600
-            except AttributeError:
+            except AttributeError as exc:
                 raise ValueError(
                     "'resolution' argument has to be nonnegative float or int"
                     + " or the given timeseries needs a datetime index"
-                )
+                ) from exc
             except TypeError:
                 try:
                     self.timeSeries.index = pd.to_datetime(self.timeSeries.index)
                     timedelta = self.timeSeries.index[1] - self.timeSeries.index[0]
                     self.resolution = float(timedelta.total_seconds()) / 3600
-                except:
+                except Exception as exc:
                     raise ValueError(
                         "'resolution' argument has to be nonnegative float or int"
                         + " or the given timeseries needs a datetime index"
-                    )
+                    ) from exc
 
         if not (isinstance(self.resolution, int) or isinstance(self.resolution, float)):
             raise ValueError("resolution has to be nonnegative float or int")