restore sys.modules

tests/test_main.py

@@ -11,6 +11,7 @@ def test_cli_calling():
 def test_do_not_import_linter():
     """When deal is imported, it must not trigger importing linter.
     """
+    old_modules = sys.modules.copy()
     for name in list(sys.modules):
         if name == 'deal' or name.startswith('deal.'):
             del sys.modules[name]
@@ -24,3 +25,5 @@ def test_do_not_import_linter():
             raise ImportError('oh no, linter was imported')
         if name == 'astroid' or name.startswith('astroid.'):
             raise ImportError('oh no, astroid was imported')
+
+    sys.modules = old_modules