[fix] assert_raises_regex(): Handle exceptions without message

Author: srittau

NEWS.rst

@@ -1,6 +1,11 @@
 News in asserts 0.8.1
 =====================
 
+Bug Fixes
+---------
+
+* `assert_raises_regex()`: Handle exceptions without any message correctly.
+
 News in asserts 0.8.0
 =====================
 

asserts/__init__.py

@@ -833,6 +833,11 @@ def assert_raises_regex(exception, regex, msg_fmt="{msg}"):
 
     def test(exc):
         compiled = re.compile(regex)
+        if not exc.args:
+            msg = "{} without message".format(exception.__name__)
+            fail(msg_fmt.format(
+                msg=msg, text=None, pattern=compiled.pattern,
+                exc_type=exception, exc_name=exception.__name__))
         text = exc.args[0]
         if not compiled.search(text):
             msg = "{!r} does not match {!r}".format(text, compiled.pattern)

test_asserts.py

@@ -806,6 +806,18 @@ def test_assert_raises_regex__exception_not_raised__custom_message(self):
             with assert_raises_regex(KeyError, r"test", msg_fmt=msg_fmt):
                 pass
 
+    def test_assert_raises_regex__no_message__default_message(self):
+        with _assert_raises_assertion("KeyError without message"):
+            with assert_raises_regex(KeyError, r"test"):
+                raise KeyError()
+
+    def test_assert_raises_regex__no_message__custom_message(self):
+        expected = "KeyError without message;KeyError;KeyError;None;test"
+        with _assert_raises_assertion(expected):
+            msg_fmt = "{msg};{exc_type.__name__};{exc_name};{text!r};{pattern}"
+            with assert_raises_regex(KeyError, r"test", msg_fmt=msg_fmt):
+                raise KeyError()
+
     def test_assert_raises_regex__wrong_exception_raised(self):
         try:
             with assert_raises_regex(IndexError, "test message"):