No one uses string exceptions anymore.

src/twisted/python/failure.py

@@ -289,9 +289,6 @@ def __init__(self, exc_value=None, exc_type=None, exc_tb=None, captureVars=False
         self.type = self.value = tb = None
         self.captureVars = captureVars
 
-        if isinstance(exc_value, str) and exc_type is None:
-            raise TypeError("Strings are not supported by Failure")
-
         stackOffset = 0
 
         if exc_value is None:

src/twisted/test/test_failure.py

@@ -398,14 +398,6 @@ def test_RaiseExceptionWithTB(self) -> None:
         innerline = self._getInnermostFrameLine(f)
         self.assertEqual(innerline, "1 / 0")
 
-    def test_stringExceptionConstruction(self) -> None:
-        """
-        Constructing a C{Failure} with a string as its exception value raises
-        a C{TypeError}, as this is no longer supported as of Python 2.6.
-        """
-        exc = self.assertRaises(TypeError, failure.Failure, "ono!")
-        self.assertIn("Strings are not supported by Failure", str(exc))
-
     def test_ConstructionFails(self) -> None:
         """
         Creating a Failure with no arguments causes it to try to discover the