[3.5] bpo-29773: Add more cases for testing string to float conversion errors. (#587)

(cherry picked from commit 9e6ac83)

Author: serhiy-storchaka

Lib/test/test_float.py

@@ -98,15 +98,27 @@ def test_float_memoryview(self):
  self.assertEqual(float(memoryview(b'12.34')[1:4]), 2.3)
 
  def test_error_message(self):
- testlist = ('\xbd', '123\xbd', ' 123 456 ')
- for s in testlist:
- try:
+ def check(s):
+ with self.assertRaises(ValueError, msg='float(%r)' % (s,)) as cm:
  float(s)
- except ValueError as e:
- self.assertIn(s.strip(), e.args[0])
- else:
- self.fail("Expected int(%r) to raise a ValueError", s)
-
+ self.assertEqual(str(cm.exception),
+ 'could not convert string to float: %r' % (s,))
+
+ check('\xbd')
+ check('123\xbd')
+ check(' 123 456 ')
+ check(b' 123 456 ')
+
+ # non-ascii digits (error came from non-digit '!')
+ check('\u0663\u0661\u0664!')
+ # embedded NUL
+ check('123\x00')
+ check('123\x00 245')
+ check('123\x00245')
+ # byte string with embedded NUL
+ check(b'123\x00')
+ # non-UTF-8 byte string
+ check(b'123\xa0')
 
  @support.run_with_locale('LC_NUMERIC', 'fr_FR', 'de_DE')
  def test_float_with_comma(self):