REV: Tidier use of ROOT in structure.py

As suggested in this [review comment](#60 (comment)), thanks.

eark_validator/structure.py

@@ -39,7 +39,7 @@
 
 METS_NAME = 'METS.xml'
 STR_REQ_PREFIX = 'CSIPSTR'
-ROOT = 'root '
+ROOT = 'root'
 DIR_NAMES = {
     'DATA': 'data',
     'DESC': 'descriptive',
@@ -154,7 +154,7 @@ def get_representations(self) -> List[Representation]:
 
     def get_root_results(self) -> List[Result]:
         results: List[Result] = []
-        location: str = ROOT + self.name
+        location: str = _root_loc(self.name)
         if not self.parser.is_archive:
             results.append(test_result_from_id(3, location))
         if not self.parser.has_mets():
@@ -195,13 +195,13 @@ def _get_schema_results(self) -> Optional[Result]:
         for tests in self.representations.values():
             if tests.has_schemas():
                 return None
-        return test_result_from_id(15, ROOT + self.name)
+        return test_result_from_id(15, _root_loc(self.name))
 
     def _get_dox_results(self) -> Optional[Result]:
         for tests in self.representations.values():
             if tests.has_documentation():
                 return None
-        return test_result_from_id(16, ROOT + self.name)
+        return test_result_from_id(16, _root_loc(self.name))
 
     @classmethod
     def get_status(cls, results: List[Result]) -> StructureStatus:
@@ -240,7 +240,10 @@ def get_bad_path_results(path) -> StructResults:
         })
 
 def _get_str1_result_list(name: str) -> List[Result]:
-    return [ test_result_from_id(1, ROOT + str(name)) ]
+    return [ test_result_from_id(1, _root_loc(name)) ]
+
+def _root_loc(name: str) -> str:
+    return f'{ROOT} {name}'
 
 def validate(to_validate) -> Tuple[bool, StructResults]:
     try: