adding a conditional wrapper to the pynumero import

pyomo/contrib/edi/formulation.py

@@ -22,10 +22,20 @@
 from pyomo.environ import Var, Param, Objective, Constraint, Set
 from pyomo.environ import maximize, minimize
 from pyomo.environ import units as pyomo_units
-from pyomo.contrib.pynumero.interfaces.external_grey_box import (
-    ExternalGreyBoxModel,
-    ExternalGreyBoxBlock,
+
+egb, egb_available = attempt_import(
+    "pyomo.contrib.pynumero.interfaces.external_grey_box"
 )
+if egb_available:
+    from pyomo.contrib.pynumero.interfaces.external_grey_box import (
+        ExternalGreyBoxModel,
+        ExternalGreyBoxBlock,
+    )
+else:
+    raise ImportError(
+        "pyomo.contrib.edi requires pyomo.contrib.pynumero to be installed to enable black box capability, this should have installed with base pyomo"
+    )
+
 from pyomo.environ import (
     Reals,
     PositiveReals,