ssl.SSLSocket.write on non-blocking sockets will fail with:

_ssl.c:1217: error:1409F07F:SSL routines:SSL3_WRITE_PENDING:bad write retry

on a write retry, if the buffer address has changed between the initial call and the retry (when the initial call returned 0 bytes written, which means you should try again later).

From OpenSSL docs (http://www.openssl.org/docs/ssl/SSL_CTX_set_mode.html):

SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER
Make it possible to retry SSL_write() with changed buffer location (the buffer contents must stay the same). This is not the default to avoid the misconception that non-blocking SSL_write() behaves like non-blocking write().

Attached patch fixes the problem (tested on Python 2.6.5, 2.7 trunk) by calling SSL_CTX_set_mode with SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER. It's a single line patch.