Remove some obsolete Twisted version checks. (#18729)

Follows: #18727
---------

Signed-off-by: Olivier 'reivilibre <oliverw@matrix.org>

Author: reivilibre

changelog.d/18729.misc

@@ -0,0 +1 @@
+Bump minimum version bound on Twisted to 21.2.0.

synapse/__init__.py

@@ -45,16 +45,6 @@
 
 # Allow using the asyncio reactor via env var.
 if strtobool(os.environ.get("SYNAPSE_ASYNC_IO_REACTOR", "0")):
-    from incremental import Version
-
-    import twisted
-
-    # We need a bugfix that is included in Twisted 21.2.0:
-    # https://twistedmatrix.com/trac/ticket/9787
-    if twisted.version < Version("Twisted", 21, 2, 0):
-        print("Using asyncio reactor requires Twisted>=21.2.0")
-        sys.exit(1)
-
     import asyncio
 
     from twisted.internet import asyncioreactor

synapse/handlers/send_email.py

@@ -24,16 +24,13 @@
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
 from io import BytesIO
-from typing import TYPE_CHECKING, Any, Dict, Optional
+from typing import TYPE_CHECKING, Dict, Optional
 
-from pkg_resources import parse_version
-
-import twisted
 from twisted.internet.defer import Deferred
 from twisted.internet.endpoints import HostnameEndpoint
-from twisted.internet.interfaces import IOpenSSLContextFactory, IProtocolFactory
+from twisted.internet.interfaces import IProtocolFactory
 from twisted.internet.ssl import optionsForClientTLS
-from twisted.mail.smtp import ESMTPSender, ESMTPSenderFactory
+from twisted.mail.smtp import ESMTPSenderFactory
 from twisted.protocols.tls import TLSMemoryBIOFactory
 
 from synapse.logging.context import make_deferred_yieldable
@@ -44,49 +41,6 @@
 
 logger = logging.getLogger(__name__)
 
-_is_old_twisted = parse_version(twisted.__version__) < parse_version("21")
-
-
-class _BackportESMTPSender(ESMTPSender):
-    """Extend old versions of ESMTPSender to configure TLS.
-
-    Unfortunately, before Twisted 21.2, ESMTPSender doesn't give an easy way to
-    disable TLS, or to configure the hostname used for TLS certificate validation.
-    This backports the `hostname` parameter for that functionality.
-    """
-
-    __hostname: Optional[str]
-
-    def __init__(self, *args: Any, **kwargs: Any) -> None:
-        """"""
-        self.__hostname = kwargs.pop("hostname", None)
-        super().__init__(*args, **kwargs)
-
-    def _getContextFactory(self) -> Optional[IOpenSSLContextFactory]:
-        if self.context is not None:
-            return self.context
-        elif self.__hostname is None:
-            return None  # disable TLS if hostname is None
-        return optionsForClientTLS(self.__hostname)
-
-
-class _BackportESMTPSenderFactory(ESMTPSenderFactory):
-    """An ESMTPSenderFactory for _BackportESMTPSender.
-
-    This backports the `hostname` parameter, to disable or configure TLS.
-    """
-
-    __hostname: Optional[str]
-
-    def __init__(self, *args: Any, **kwargs: Any) -> None:
-        self.__hostname = kwargs.pop("hostname", None)
-        super().__init__(*args, **kwargs)
-
-    def protocol(self, *args: Any, **kwargs: Any) -> ESMTPSender:  # type: ignore
-        # this overrides ESMTPSenderFactory's `protocol` attribute, with a Callable
-        # instantiating our _BackportESMTPSender, providing the hostname parameter
-        return _BackportESMTPSender(*args, **kwargs, hostname=self.__hostname)
-
 
 async def _sendmail(
     reactor: ISynapseReactor,
@@ -129,9 +83,7 @@ async def _sendmail(
     elif tlsname is None:
         tlsname = smtphost
 
-    factory: IProtocolFactory = (
-        _BackportESMTPSenderFactory if _is_old_twisted else ESMTPSenderFactory
-    )(
+    factory: IProtocolFactory = ESMTPSenderFactory(
         username,
         password,
         from_addr,