[property] Specify ValueError Message

If format of value is wrong, e.g. with date, more info is given.

Author: fschrader1992

odml/property.py

@@ -247,6 +247,9 @@ def _validate_values(self, values):
             try:
                 dtypes.get(v, self.dtype)
             except Exception:
+                raise ValueError("odml.Property.values: passed value \'%s\' are not of "
+                                 "consistent type \'%s\'! Format should be \'%s\'." %
+                                 (v, self._dtype, dtypes.default_values(self._dtype)))
                 return False
         return True
 
@@ -327,9 +330,7 @@ def values(self, new_value):
         if self._dtype is None:
             self._dtype = dtypes.infer_dtype(new_value[0])
 
-        if not self._validate_values(new_value):
-            raise ValueError("odml.Property.values: passed values are not of "
-                             "consistent type!")
+        self._validate_values(new_value)
         self._values = [dtypes.get(v, self.dtype) for v in new_value]
 
     @property