Python 3.10 partial support

Everything below is specific to changes in Python 3.10.
https://github.com/eventlet/eventlet/pull/715

- Only wrap socket.timeout on Python < 3.10
  socket.timeout is TimeoutError, which our is_timeout() helper func already knows.
  fixes https://github.com/eventlet/eventlet/issues/687
- Working greenio._open
  _pyio.open is now a staticmethod, so we've got to go down to
  _pyio.open.__wrapped__ to get to the python function object.
- Test using eventlet.is_timeout rather than requiring an is_timeout attribute on errors.
  TimeoutErrors (which are covered by is_timeout) can't necessarily have attributes added to them.
- Fix backdoor tests
  Skip build info line at interpreter startup. Also, start printing the banner as we read it to aid in future debugging.
- Tolerate __builtins__ being a dict (rather than module) in is_timeout
  (@tipabu) still not sure how this happens, but somehow it does in socket_test.test_error_is_timeout.

2 files changed, 5 insertions, 2 deletions

diff --git a/tests/__init__.py b/tests/__init__.py
index c0b64fd..1883667 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -383,7 +383,7 @@ def run_isolated(path, prefix='tests/isolated/', **kwargs):
 
 def check_is_timeout(obj):
     value_text = getattr(obj, 'is_timeout', '(missing)')
-    assert obj.is_timeout, 'type={0} str={1} .is_timeout={2}'.format(type(obj), str(obj), value_text)
+    assert eventlet.is_timeout(obj), 'type={0} str={1} .is_timeout={2}'.format(type(obj), str(obj), value_text)
 
 
 @contextlib.contextmanager
diff --git a/tests/backdoor_test.py b/tests/backdoor_test.py
index 03a5692..1e09f09 100644
--- a/tests/backdoor_test.py
+++ b/tests/backdoor_test.py
@@ -1,5 +1,6 @@
 import os
 import os.path
+import sys
 
 import eventlet
 
@@ -22,7 +23,9 @@ class BackdoorTest(tests.LimitedTestCase):
     def _run_test_on_client_and_server(self, client, server_thread):
         f = client.makefile('rw')
         assert 'Python' in f.readline()
-        f.readline()  # build info
+        if sys.version_info < (3, 10):
+            # Starting in py310, build info is included in version line
+            f.readline()  # build info
         f.readline()  # help info
         assert 'InteractiveConsole' in f.readline()
         self.assertEqual('>>> ', f.read(4))