Do not support patch_sys under Py3 because of differences in the interpreter...

Do not support patch_sys under Py3 because of differences in the interpreter that make the current approach using a threadpool unworkable. Fixes test__issue6.

gevent/fileobject.py

@@ -307,6 +307,7 @@ class FileObjectThread(object):
         if line:
             return line
         raise StopIteration
+    __next__ = next
 
 
 FileObjectClosed = IOError(EBADF, 'Bad file descriptor (FileObject was closed)')

gevent/monkey.py

@@ -17,9 +17,11 @@ __all__ = ['patch_all',
 
 if sys.version_info[0] >= 3:
     string_types = str,
+    PY3 = True
 else:
     import __builtin__
     string_types = __builtin__.basestring
+    PY3 = False
 
 
 # maps module name -> attribute name -> original item
@@ -85,6 +87,20 @@ def _patch_sys_std(name):
 
 
 def patch_sys(stdin=True, stdout=True, stderr=True):
+    """Patch sys.std[in,out,err] to use a cooperative IO via a threadpool.
+
+    This is relatively dangerous and can have unintended consequences such as hanging
+    the process or misinterpreting control keys.
+
+    This method does nothing on Python 3. The Python 3 interpreter wants to flush
+    the TextIOWrapper objects that make up stderr/stdout at shutdown time, but
+    using a threadpool at that time leads to a hang.
+    """
+    # test__issue6.py demonstrates the hang if these lines are removed;
+    # strangely enough that test passes even without monkey-patching sys
+    if PY3:
+        return
+
     if stdin:
         _patch_sys_std('stdin')
     if stdout:

greentest/test__issue6.py

@@ -8,8 +8,8 @@ if not sys.argv[1:]:
     out, err = p.communicate(b'hello world\n')
     code = p.poll()
     assert p.poll() == 0, (out, err, code)
-    assert out.strip() == '11 chars.', (out, err, code)
-    assert err == '', (out, err, code)
+    assert out.strip() == b'11 chars.', (out, err, code)
+    assert err == b'', (out, err, code)
 
 elif sys.argv[1:] == ['subprocess']:
     import gevent

known_failures.py

@@ -11,8 +11,6 @@ PY3 = sys.version_info[0] >= 3
 
 
 FAILING_TESTS = [
-    # needs investigating
-    'FLAKY test__issue6.py',
 
     # Sometimes fails with AssertionError: ...\nIOError: close() called during concurrent operation on the same file object.\n'
     # Sometimes it contains "\nUnhandled exception in thread started by \nsys.excepthook is missing\nlost sys.stderr\n"