MINOR: named_defaults: return different error when from is missing

Author: mjuraga

errors/parse.go

@@ -53,3 +53,5 @@ var ErrSectionTypeNotAllowed = errors.New("section type not allowed")
 var ErrScopeMissing = errors.New("scope missing")
 
 var ErrScopeAlreadyExists = errors.New("scope already exists")
+
+var ErrFromDefaultsSectionMissing = errors.New("defaults section specified in from does not exist")

fetch.go

@@ -205,7 +205,7 @@ func (p *configParser) SectionsDefaultsFromSet(sectionType Section, sectionName,
 		}
 		_, ok = stDef[defaultsSection]
 		if !ok {
-			return errors.ErrSectionMissing
+			return errors.ErrFromDefaultsSectionMissing
 		}
 	}
 	section.DefaultSectionName = defaultsSection