Fix string formatting TypeError if tuple is passed

Fixed issue where the "ambiguous literal" error message used when
interpreting literal values as SQL expression values would encounter a
tuple value, and fail to format the message properly. Pull request courtesy
Miguel Ventura.

Change-Id: I50d5d32d5f80ec79703a42d4b19b42c2f9701f24
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/442

1 files changed, 15 insertions, 3 deletions

diff --git a/test/sql/test_case_statement.py b/test/sql/test_case_statement.py
index f7025b360..d81ff20cd 100644
--- a/test/sql/test_case_statement.py
+++ b/test/sql/test_case_statement.py
@@ -1,4 +1,4 @@
-from sqlalchemy.testing import assert_raises, eq_
+from sqlalchemy.testing import assert_raises, eq_, assert_raises_message
 from sqlalchemy.testing import fixtures, AssertsCompiledSQL
 from sqlalchemy import (
     testing, exc, case, select, literal_column, text, and_, Integer, cast,
@@ -102,11 +102,23 @@ class CaseTest(fixtures.TestBase, AssertsCompiledSQL):
             (0, 6, 'pk_6_data')
         ]
 
+    def test_literal_interpretation_ambiguous(self):
+        assert_raises_message(
+            exc.ArgumentError,
+            r"Ambiguous literal: 'x'.  Use the 'text\(\)' function",
+            case, [("x", "y")]
+        )
+
+    def test_literal_interpretation_ambiguous_tuple(self):
+        assert_raises_message(
+            exc.ArgumentError,
+            r"Ambiguous literal: \('x', 'y'\).  Use the 'text\(\)' function",
+            case, [(("x", "y"), "z")]
+        )
+
     def test_literal_interpretation(self):
         t = table('test', column('col1'))
 
-        assert_raises(exc.ArgumentError, case, [("x", "y")])
-
         self.assert_compile(
             case([("x", "y")], value=t.c.col1),
             "CASE test.col1 WHEN :param_1 THEN :param_2 END")