fix: directory is not package unless contains metadata file (#7)

iter_packages previously considered any directory in a package_path
to be a package.
This adds a check that the metadata.path is a file before considering
the directory to be a package.

src/monas/config.py

@@ -90,7 +90,11 @@ def iter_packages(self) -> Iterable[PyPackage]:
         for p in self.package_paths:
             for package in p.iterdir():
                 if package.is_dir():
-                    yield PyPackage(self, package)
+                    pypackage = PyPackage(self, package)
+                    if not pypackage.metadata.path.is_file():
+                        # directory has no python metadata file, ignore
+                        continue
+                    yield pypackage
 
 
 pass_config = click.make_pass_decorator(Config, ensure=True)