adressing creationtime=None

cal_tools/cal_tools/tools.py

@@ -482,10 +482,14 @@ def get_from_db(device, constant, condition, empty_constant,
         metadata = ConstantMetaData()
         metadata.calibration_constant = constant
         metadata.detector_condition = condition
+        when = None
         if creation_time is None:
             metadata.calibration_constant_version = Versions.Now(
                                                     device=device)
         else:
+            if hasattr(creation_time, 'isoformat'):
+                when = creation_time.isoformat()
+
             metadata.calibration_constant_version = Versions.Timespan(
                                                     device=device,
                                                     start=creation_time)
@@ -498,7 +502,7 @@ def get_from_db(device, constant, condition, empty_constant,
                                                          device))
                 
                 r = metadata.retrieve(this_interface, timeout=timeout,
-                                      when=creation_time.isoformat(),
+                                      when=when,
                                       meta_only=meta_only,
                                       version_info=version_info)
                 if version_info: