Paho-mqtt

===================

- Fix hang when client restarted and broker resumed a session with Qos2
message. Closes 284.
Note: this change replace the hang by a message lost ! See README for
current limitation of paho-mqtt.
- Fix reconnection loop when a clean_session=True client reconnect while Qos2
message are being sent.
Note: this change replace the infinite reconnection loop by a possible
duplicate QoS2 message. Only clean_session=True client are affected, see
README for current limitation of paho-mqtt.
- Catch and log any exception raised by user callback. Closes 294.
- Improve support for external event loop (like asyncio). Closes 235.
- Fix order of message with publish.multiple helper. Closes 87.
- Fix hang on wait_for_published() on bad network. Closes 309.
- Fix an issue with Websocket that seems to happen only on Windows.
Closes 268.
- Fix issue with Websocket payload size between 127 and 65536. Closes 267.
- Closes socket in client destructor to avoid FD leak. Closes 170.
- Fix uncaught timeout exception during connection. Closes 288.
- Remove dup flag on PUBREL packet. Closes 298.
- Use secure entropy source for Websocket mask_key (urandom). Closes 305.
- Fix mid generation that was not thread-safe.
- Replace print() statements with proper logging. Closes 214.
- Allow insecure TLS on publish and subscribe helpers. Closes 299.
- Allow to remove authentication (reset username to None). Closes 259.
- Add support for the non-standard bridge mode. Closes 282.

===================

- Fix reconnect_delay_set which ignored the max_delay. Closes 218.
- Fix crash when connection is lost while trying to send message. Closes 208.
- Fix issue with unicode topic when some character were multi-bytes UTF-8.
- Fix issue with empty Client ID with broker that don't support them. Closes 209.
- Fix issue with tls_set that did not allowed cert_reqs=ssl.CERT_NONE.
Closes 123.
- Relax requirement on pytest-runner, it's now only required for tests. Closes
207, 227.

===================

- **BREAKING** Requires Python 2.7 or 3.4+. Closes 163.
- **BREAKING** Remove support for SSL without SSLContext (Requires Python 2.7.9+ or 3.2+).
Closes 115.
- **BREAKING** on_connect callback is now always called flags. Previously this
callback could accepts 3 OR 4 arguments, now it must accepts 4. Closes 197.
- **BREAKING** tls_insecure_set() must now be called *after* tls_set()
- Allow username and password to be zero length (as opposed to not being
present). Closes 80.
- Allow zero length client ids when using MQTT v3.1.1.
- Add SSLContext support, including SNI. Closes 11.
- Improved support for unicode topic and binary payload.
Closes 15, 16.
- Allow arbitrary Websocket headers and path.
Closes 169.
- Fix issue with large inbound payload over Websocket. Closes 107.
- Add exponential delay for reconnection. Closes 195.
- Move unit tests to pytest (164) and tox (187)
- Add support for standard Python logging. Closes 95.
- Fix duplicate incoming QoS==2 message. Closes 194.

===================

- Fix possible hang of TLS connection during handshake.
Closes 3.
- Fix issue with publish helper with TLS connection.
Closes 180.
- Fix installation issue on non-UTF-8 system.
Closes 181.
- Fix non-working Websocket over TLS connection.
Closes 182.

===================

- Fix message lost when using paho.mqtt.publish helper with QoS=0 message.
Closes 172.

===================

- Handle unicode username and passwords correctly. Closes 79.
- Fix handling of invalid UTF-8 topics on incoming messages - the library now
does not attempt to decode the topic - this will happen when the user
accesses msg.topic in the on_message callback. If the topic is not valid
UTF-8, an exception will be raised. Closes 75.
- Fix issue with WebSocket connection in case of network issue (timeout or
connection broken). Closes 105.
- Fix issue with SSL connection, where latest incoming message may be delayed
or never processed. Closes 131.
- Fix possible message lost with publish.single and publish.multiple. Closes
119.