add option for delayed imports

will make setup checking easier, although it does not work for all cases
(from imports for example)

Change-Id: I2e5cf9b427a6f8e6f603d9662cdb9700d5f9ad9a
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/33893
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>
Reviewed-by: Alexander Zaft <a.zaft@fz-juelich.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>

frappy_mlz/seop.py

@@ -24,17 +24,17 @@
 
 from os import path
 
-# eventually he3control
-from he3d import he3cell  # pylint: disable=import-error
-
 from frappy.core import Attached
 from frappy.datatypes import ArrayOf, FloatRange, IntRange, StatusType, \
     StringType, TupleOf
 from frappy.errors import CommandRunningError
+from frappy.lib import delayed_import
 from frappy.modules import Command, Drivable, Module, Parameter, Property, \
     Readable
 from frappy.rwhandler import CommonReadHandler
 
+he3d = delayed_import('he3d')
+
 integral = IntRange()
 floating = FloatRange()
 string = StringType()
@@ -52,7 +52,7 @@ class Cell(Module):
 
     def initModule(self):
         super().initModule()
-        self.cell = he3cell.He3_cell(
+        self.cell = he3d.he3cell.He3_cell(
             path.join(self.config_directory, 'cell.yml'))
 
     # Commands