Index: Lib/difflib.py
===================================================================
--- Lib/difflib.py	(revision 88766)
+++ Lib/difflib.py	(working copy)
@@ -1198,14 +1198,26 @@
         for tag, i1, i2, j1, j2 in group:
             if tag == 'equal':
                 for line in a[i1:i2]:
-                    yield ' ' + line
+                    if not line.endswith(lineterm):
+                        yield ' ' + line + lineterm
+                        yield r'\ No newline at end of file' + lineterm
+                    else:
+                        yield ' ' + line
                 continue
             if tag == 'replace' or tag == 'delete':
                 for line in a[i1:i2]:
-                    yield '-' + line
+                    if not line.endswith(lineterm):
+                        yield '-' + line + lineterm
+                        yield r'\ No newline at end of file' + lineterm
+                    else:
+                        yield '-' + line
             if tag == 'replace' or tag == 'insert':
                 for line in b[j1:j2]:
-                    yield '+' + line
+                    if not line.endswith(lineterm):
+                        yield '+' + line + lineterm
+                        yield r'\ No newline at end of file' + lineterm
+                    else:
+                        yield '+' + line
 
 # See http://www.unix.org/single_unix_specification/
 def context_diff(a, b, fromfile='', tofile='',
@@ -1272,7 +1284,11 @@
             for tag, i1, i2, _, _ in group:
                 if tag != 'insert':
                     for line in a[i1:i2]:
-                        yield prefixmap[tag] + line
+                        if not line.endswith(lineterm):
+                            yield prefixmap[tag] + line + lineterm
+                            yield r'\ No newline at end of file' + lineterm
+                        else:
+                            yield prefixmap[tag] + line
 
         if group[-1][4] - group[0][3] >= 2:
             yield '--- %d,%d ----%s' % (group[0][3]+1, group[-1][4], lineterm)
@@ -1283,7 +1299,11 @@
             for tag, _, _, j1, j2 in group:
                 if tag != 'delete':
                     for line in b[j1:j2]:
-                        yield prefixmap[tag] + line
+                        if not line.endswith(lineterm):
+                            yield prefixmap[tag] + line + lineterm
+                            yield r'\ No newline at end of file' + lineterm
+                        else:
+                            yield prefixmap[tag] + line
 
 def ndiff(a, b, linejunk=None, charjunk=IS_CHARACTER_JUNK):
     r"""
Index: Lib/test/test_difflib.py
===================================================================
--- Lib/test/test_difflib.py	(revision 88766)
+++ Lib/test/test_difflib.py	(working copy)
@@ -237,12 +237,55 @@
         self.assertEqual(list(cd)[0:2], ["*** Original", "--- Current"])
 
 
+class TestNoNewLineAtEnd(unittest.TestCase):
+    """ Test no newline at end of file, from issue2142 """
+    def test_unified_diff(self):
+        lines = list(difflib.unified_diff(
+            "one\ntwo\nthree".splitlines(1),
+            "one\ntwo\ntrois".splitlines(1),
+            "Before", "After"))
+        expected = [
+            '--- Before\n',
+            '+++ After\n',
+            '@@ -1,3 +1,3 @@\n',
+            ' one\n',
+            ' two\n',
+            '-three\n',
+            '\\ No newline at end of file\n',
+            '+trois\n',
+            '\\ No newline at end of file\n'
+        ]
+        self.assertEqual(lines, expected)
+
+    def test_context_diff(self):
+        lines = list(difflib.context_diff(
+            "one\ntwo\nthree".splitlines(1),
+            "one\ntwo\ntrois".splitlines(1),
+            "Before", "After"))
+        expected = [
+            '*** Before\n',
+            '--- After\n',
+            '***************\n',
+            '*** 1,3 ****\n',
+            '  one\n',
+            '  two\n',
+            '! three\n',
+            '\\ No newline at end of file\n',
+            '--- 1,3 ----\n',
+            '  one\n',
+            '  two\n',
+            '! trois\n',
+            '\\ No newline at end of file\n',
+        ]
+        self.assertEqual(lines, expected)
+
+
 def test_main():
     difflib.HtmlDiff._default_prefix = 0
     Doctests = doctest.DocTestSuite(difflib)
     run_unittest(
         TestWithAscii, TestAutojunk, TestSFpatches, TestSFbugs,
-        TestOutputFormat, Doctests)
+        TestOutputFormat, TestNoNewLineAtEnd, Doctests)
 
 if __name__ == '__main__':
     test_main()