*: Remove references to old python versions

Mainly in docs that say things like "you can only use this if you're
using python 3.2".

tornado/gen.py

@@ -275,6 +275,10 @@ def is_coroutine_function(func: Any) -> bool:
 class Return(Exception):
     """Special exception to return a value from a `coroutine`.
 
+    This exception exists for compatibility with older versions of
+    Python (before 3.3). In newer code use the ``return`` statement
+    instead.
+
     If this exception is raised, its value argument is used as the
     result of the coroutine::
 
@@ -283,14 +287,7 @@ def fetch_json(url):
             response = yield AsyncHTTPClient().fetch(url)
             raise gen.Return(json_decode(response.body))
 
-    In Python 3.3, this exception is no longer necessary: the ``return``
-    statement can be used directly to return a value (previously
-    ``yield`` and ``return`` with a value could not be combined in the
-    same function).
-
-    By analogy with the return statement, the value argument is optional,
-    but it is never necessary to ``raise gen.Return()``.  The ``return``
-    statement can be used with no arguments instead.
+    By analogy with the return statement, the value argument is optional.
     """
 
     def __init__(self, value: Any = None) -> None:
@@ -337,7 +334,7 @@ class WaitIterator:
     arguments were used in the construction of the `WaitIterator`,
     ``current_index`` will use the corresponding keyword).
 
-    On Python 3.5, `WaitIterator` implements the async iterator
+    `WaitIterator` implements the async iterator
     protocol, so it can be used with the ``async for`` statement (note
     that in this version the entire iteration is aborted if any value
     raises an exception, while the previous example can continue past

tornado/iostream.py

@@ -1147,8 +1147,7 @@ class is recommended instead of calling this method directly.
 
         In SSL mode, the ``server_hostname`` parameter will be used
         for certificate validation (unless disabled in the
-        ``ssl_options``) and SNI (if supported; requires Python
-        2.7.9+).
+        ``ssl_options``) and SNI.
 
         Note that it is safe to call `IOStream.write
         <BaseIOStream.write>` while the connection is pending, in
@@ -1381,12 +1380,6 @@ def _do_ssl_handshake(self) -> None:
                 )
                 return self.close(exc_info=err)
             raise
-        except ssl.CertificateError as err:
-            # CertificateError can happen during handshake (hostname
-            # verification) and should be passed to user. Starting
-            # in Python 3.7, this error is a subclass of SSLError
-            # and will be handled by the previous block instead.
-            return self.close(exc_info=err)
         except OSError as err:
             # Some port scans (e.g. nmap in -sT mode) have been known
             # to cause do_handshake to raise EBADF and ENOTCONN, so make

tornado/netutil.py

@@ -501,10 +501,6 @@ def initialize(self) -> None:  # type: ignore
 class ThreadedResolver(ExecutorResolver):
     """Multithreaded non-blocking `Resolver` implementation.
 
-    Requires the `concurrent.futures` package to be installed
-    (available in the standard library since Python 3.2,
-    installable with ``pip install futures`` in older versions).
-
     The thread pool size can be configured with::
 
         Resolver.configure('tornado.netutil.ThreadedResolver',
@@ -598,17 +594,15 @@ def ssl_options_to_context(
     """Try to convert an ``ssl_options`` dictionary to an
     `~ssl.SSLContext` object.
 
-    The ``ssl_options`` dictionary contains keywords to be passed to
-    ``ssl.SSLContext.wrap_socket``.  In Python 2.7.9+, `ssl.SSLContext` objects can
-    be used instead.  This function converts the dict form to its
-    `~ssl.SSLContext` equivalent, and may be used when a component which
-    accepts both forms needs to upgrade to the `~ssl.SSLContext` version
-    to use features like SNI or NPN.
+    The ``ssl_options`` argument may be either an `ssl.SSLContext` object or a dictionary containing
+    keywords to be passed to ``ssl.SSLContext.wrap_socket``.  This function converts the dict form
+    to its `~ssl.SSLContext` equivalent, and may be used when a component which accepts both forms
+    needs to upgrade to the `~ssl.SSLContext` version to use features like SNI or ALPN.
 
     .. versionchanged:: 6.2
 
-       Added server_side argument. Omitting this argument will
-       result in a DeprecationWarning on Python 3.10.
+       Added server_side argument. Omitting this argument will result in a DeprecationWarning on
+       Python 3.10.
 
     """
     if isinstance(ssl_options, ssl.SSLContext):

tornado/options.py

@@ -482,15 +482,11 @@ def run_parse_callbacks(self) -> None:
 
     def mockable(self) -> "_Mockable":
         """Returns a wrapper around self that is compatible with
-        `mock.patch <unittest.mock.patch>`.
+        `unittest.mock.patch`.
 
-        The `mock.patch <unittest.mock.patch>` function (included in
-        the standard library `unittest.mock` package since Python 3.3,
-        or in the third-party ``mock`` package for older versions of
-        Python) is incompatible with objects like ``options`` that
-        override ``__getattr__`` and ``__setattr__``.  This function
-        returns an object that can be used with `mock.patch.object
-        <unittest.mock.patch.object>` to modify option values::
+        The `unittest.mock.patch` function is incompatible with objects like ``options`` that
+        override ``__getattr__`` and ``__setattr__``.  This function returns an object that can be
+        used with `mock.patch.object <unittest.mock.patch.object>` to modify option values::
 
             with mock.patch.object(options.mockable(), 'name', value):
                 assert options.name == value
@@ -664,9 +660,8 @@ def _parse_timedelta(self, value: str) -> datetime.timedelta:
                 num = float(m.group(1))
                 units = m.group(2) or "seconds"
                 units = self._TIMEDELTA_ABBREV_DICT.get(units, units)
-                # This line confuses mypy when setup.py sets python_version=3.6
-                # https://github.com/python/mypy/issues/9676
-                sum += datetime.timedelta(**{units: num})  # type: ignore
+
+                sum += datetime.timedelta(**{units: num})
                 start = m.end()
             return sum
         except Exception:

tornado/tcpserver.py

@@ -339,7 +339,7 @@ def handle_stream(
 
     def _handle_connection(self, connection: socket.socket, address: Any) -> None:
         if self.ssl_options is not None:
-            assert ssl, "Python 2.6+ and OpenSSL required for SSL"
+            assert ssl, "OpenSSL required for SSL"
             try:
                 connection = ssl_wrap_socket(
                     connection,

tornado/test/__main__.py

@@ -1,6 +1,4 @@
 """Shim to allow python -m tornado.test.
-
-This only works in python 2.7+.
 """
 
 from tornado.test.runtests import all, main

tornado/test/gen_test.py

@@ -441,7 +441,6 @@ def f():
 
     @gen_test
     def test_async_return_no_value(self):
-        # Without a return value we don't need python 3.3.
         @gen.coroutine
         def f():
             yield gen.moment

tornado/test/iostream_test.py

@@ -1078,8 +1078,6 @@ def test_handshake_fail(self):
     @gen_test
     def test_check_hostname(self):
         # Test that server_hostname parameter to start_tls is being used.
-        # The check_hostname functionality is only available in python 2.7 and
-        # up and in python 3.4 and up.
         server_future = self.server_start_tls(_server_ssl_options())
         with ExpectLog(gen_log, "SSL Error"):
             client_future = self.client_start_tls(

tornado/test/web_test.py

@@ -367,7 +367,7 @@ def test_cookie_special_char(self):
         self.assertEqual(len(headers), 3)
         self.assertEqual(headers[0], 'equals="a=b"; Path=/')
         self.assertEqual(headers[1], 'quote="a\\"b"; Path=/')
-        # python 2.7 octal-escapes the semicolon; older versions leave it alone
+        # Semicolons are octal-escaped
         self.assertIn(
             headers[2],
             ('semicolon="a;b"; Path=/', 'semicolon="a\\073b"; Path=/'),
@@ -1888,12 +1888,8 @@ def test_clear_all_cookies(self):
         response = self.fetch("/", headers={"Cookie": "foo=bar; baz=xyzzy"})
         set_cookies = sorted(response.headers.get_list("Set-Cookie"))
         # Python 3.5 sends 'baz="";'; older versions use 'baz=;'
-        self.assertTrue(
-            set_cookies[0].startswith("baz=;") or set_cookies[0].startswith('baz="";')
-        )
-        self.assertTrue(
-            set_cookies[1].startswith("foo=;") or set_cookies[1].startswith('foo="";')
-        )
+        self.assertTrue(set_cookies[0].startswith('baz="";'))
+        self.assertTrue(set_cookies[1].startswith('foo="";'))
 
 
 class PermissionError(Exception):