Sort items in join_dict, to guarantee a stable order for unit tests.

Since Python 3.7, dict.items() guarantees insertion order, but before,
the order is undefined. To have reproducible output for tests, the
params are now sorted lexicographically.

Author: cypheon

PySpice/Tools/StringTools.py

@@ -65,5 +65,5 @@ def join_list(items):
 
 def join_dict(d):
     return ' '.join(["{}={}".format(key, str_spice(value))
-                     for key, value in d.items()
+                     for key, value in sorted(d.items())
                      if value is not None])