Forgot to add builtins.

gevent/builtins.py

+# Copyright (c) 2015 gevent contributors. See LICENSE for details.
+"""gevent friendly implementations of builtin functions."""
+from __future__ import absolute_import
+
+import imp
+import sys
+import gevent.lock
+try:
+    import builtins
+    allowed_module_name_types = (str,)
+    __target__ = 'builtins'
+except ImportError: # Py2
+    import __builtin__ as builtins
+    allowed_module_name_types = (basestring,)
+    __target__ = '__builtin__'
+
+_import = builtins.__import__
+
+# We need to protect imports both across threads and across greenlets.
+# And the order matters. Note that under 3.4, the global import lock
+# and imp module are deprecated. It seems that in all Py3 versions, a
+# module lock is used such that this fix is not necessary.
+_g_import_lock = gevent.lock.RLock()
+
+
+def __import__(*args, **kwargs):
+    """
+    Normally python protects imports against concurrency by doing some locking
+    at the C level (at least, it does that in CPython).  This function just
+    wraps the normal __import__ functionality in a recursive lock, ensuring that
+    we're protected against greenlet import concurrency as well.
+    """
+    if len(args) > 0 and not issubclass(type(args[0]), allowed_module_name_types):
+        # if a builtin has been acquired as a bound instance method,
+        # python knows not to pass 'self' when the method is called.
+        # No such protection exists for monkey-patched builtins,
+        # however, so this is necessary.
+        args = args[1:]
+    imp.acquire_lock()
+    _g_import_lock.acquire()
+    try:
+        result = _import(*args, **kwargs)
+    finally:
+        _g_import_lock.release()
+        imp.release_lock()
+    return result
+
+
+if sys.version_info[:2] < (3, 3):
+    __implements__ = []
+else:
+    __implements__ = ['__import__']
+__all__ = __implements__