Fix external command for % character. (#627)

Author: jrood-nrel

manager/manager_utils.py

@@ -37,7 +37,7 @@ def pruned_spec_string(spec, variants_to_omit=["ipo", "dev_path=", "patches=", "
     full_spec = spec.format("{name}{@version}{variants}{%compiler}")
 
     # add spaces between variants so we can filter
-    spec_components = full_spec.replace("+", " +").replace("~", " ~").split(" ")
+    spec_components = full_spec.replace("+", " +").replace("%", " %").replace("~", " ~").split(" ")
 
     def filter_func(entry):
         for v in variants_to_omit: