fixed unresolved reference (#303)

* fixed unresolved reference

* fixed code formatting

tests/test_poetry.py

@@ -2,6 +2,9 @@
 from __future__ import absolute_import
 from __future__ import unicode_literals
 
+import pytest
+
+from poetry.exceptions import InvalidProjectFile
 from poetry.poetry import Poetry
 from poetry.utils._compat import Path
 from poetry.utils.toml_file import TomlFile
@@ -125,3 +128,11 @@ def test_check():
     content = complete.read()["tool"]["poetry"]
 
     assert Poetry.check(content)
+
+
+def test_check_fails():
+    complete = TomlFile(fixtures_dir / "complete.toml")
+    content = complete.read(raw=True)["tool"]["poetry"]
+    content["this key is not in the schema"] = ""
+    with pytest.raises(InvalidProjectFile):
+        Poetry.check(content)