Handle nested wildcards in package includes correctly. Fixes: #1379.

Use compat `Path`.

poetry/masonry/utils/package_include.py

@@ -44,10 +44,10 @@ def check_elements(self):  # type: () -> PackageInclude
             # Probably glob
             self._is_package = True
 
-            # The __init__.py file should be first
+            # Packages no longer need an __init__.py in python3
             root = self._elements[0]
-            if root.name != "__init__.py":
-                raise ValueError("{} is not a package.".format(root))
+            if root.name == "__init__.py":
+                pass
 
             self._package = root.parent.name
         else:

tests/masonry/utils/test_package_include.py

@@ -0,0 +1,32 @@
+from poetry.masonry.utils.package_include import PackageInclude
+from poetry.utils._compat import Path
+
+
+fixtures_dir = Path(__file__).parent / "fixtures"
+with_includes = fixtures_dir / "with_includes"
+
+
+def test_package_include_with_multiple_dirs():
+    pkg_include = PackageInclude(base=fixtures_dir, include="with_includes")
+    assert pkg_include.elements == [
+        with_includes / "__init__.py",
+        with_includes / "bar",
+        with_includes / "bar/baz.py",
+        with_includes / "extra_package",
+        with_includes / "extra_package/some_dir",
+        with_includes / "extra_package/some_dir/foo.py",
+        with_includes / "extra_package/some_dir/quux.py",
+    ]
+
+
+def test_package_include_with_simple_dir():
+    pkg_include = PackageInclude(base=with_includes, include="bar")
+    assert pkg_include.elements == [with_includes / "bar/baz.py"]
+
+
+def test_package_include_with_nested_dir():
+    pkg_include = PackageInclude(base=with_includes, include="extra_package/**/*.py")
+    assert pkg_include.elements == [
+        with_includes / "extra_package/some_dir/foo.py",
+        with_includes / "extra_package/some_dir/quux.py",
+    ]