Raise NotImplementedError properly

Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

Author: pombredanne

src/packagedcode/alpine.py

@@ -770,7 +770,7 @@ def parse_pkginfo(location):
         depend = imagemagick
 
     """
-    raise NotImplementedError('TODO: implement me')
+    raise NotImplementedError
 
 
 def build_package_data(package_fields, datasource_id, package_type):

src/packagedcode/debian_copyright.py

@@ -261,28 +261,28 @@ def from_file(cls, *args, **kwargs):
         """
         Return a DebianDetector object with License and Copyright detections.
         """
-        return NotImplementedError
+        raise NotImplementedError
 
     def get_copyright(self, *args, **kwargs):
         """
         Return a copyright string (found in Copyright: structured fields or in
         plain text).
         """
-        return NotImplementedError
+        raise NotImplementedError
 
     def get_license_expression(self, *args, **kwargs):
         """
         Return a license expression string suitable to use as a
         PackageData.license_expression.
         """
-        return NotImplementedError
+        raise NotImplementedError
 
     def get_declared_license(self, *args, **kwargs):
         """
         Return a list of declared license string suitable to use as a
         PackageData.declared_license.
         """
-        return NotImplementedError
+        raise NotImplementedError
 
 
 @attr.s