### Steps to reproduce
#### Case 1
1. updater.start_polling(clean=True)
2. Teleg…ram API returns Too Many Requests: retry after 1 (429)
#### Case 2
1. updater.start_polling(clean=False)
2. No errors
### Expected behaviour
No exception or errors from Telegram API with clean True or False
### Actual behaviour
Too Many Requests from Telegram API if clean=True
No errors if clean=False
### Configuration
**Operating System:**
Ubuntu 16.04, Debian Jessie
**Version of Python, python-telegram-bot & dependencies:**
`$ python -m telegram`
```
python-telegram-bot 5.1.0
urllib3 1.16
certifi 2016.08.08
future 0.15.2
Python 3.5.2 (default, Jul 5 2016, 12:43:10) [GCC 5.4.0 20160609]
```
```
python-telegram-bot 5.0.0
urllib3 1.16
certifi 2016.02.28
future 0.15.2
Python 3.4.2 (default, Oct 8 2014, 10:45:20) [GCC 4.9.1]
```
### Logs
```
2016-09-25 00:03:46,616 - telegram.ext.updater - ERROR - error in bootstrap phase; try=0 max_retries=0
Traceback (most recent call last):
File "/usr/local/lib/python3.5/dist-packages/telegram/ext/updater.py", line 331, in _bootstrap
self.bot.setWebhook(webhook_url=webhook_url, certificate=cert)
File "/usr/local/lib/python3.5/dist-packages/telegram/bot.py", line 126, in decorator
result = func(self, *args, **kwargs)
File "/usr/local/lib/python3.5/dist-packages/telegram/bot.py", line 1264, in setWebhook
result = self._request.post(url, data, timeout=kwargs.get('timeout'))
File "/usr/local/lib/python3.5/dist-packages/telegram/utils/request.py", line 201, in post
**urlopen_kwargs)
File "/usr/local/lib/python3.5/dist-packages/telegram/utils/request.py", line 152, in _request_wrapper
raise NetworkError('{0} ({1})'.format(message, resp.status))
telegram.error.NetworkError: Too Many Requests: retry after 1 (429)
2016-09-25 00:03:46,617 - telegram.ext.updater - ERROR - unhandled exception
Traceback (most recent call last):
File "/usr/local/lib/python3.5/dist-packages/telegram/ext/updater.py", line 117, in _thread_wrapper
target(*args, **kwargs)
File "/usr/local/lib/python3.5/dist-packages/telegram/ext/updater.py", line 228, in _start_polling
self._bootstrap(bootstrap_retries, clean=clean, webhook_url='')
File "/usr/local/lib/python3.5/dist-packages/telegram/ext/updater.py", line 331, in _bootstrap
self.bot.setWebhook(webhook_url=webhook_url, certificate=cert)
File "/usr/local/lib/python3.5/dist-packages/telegram/bot.py", line 126, in decorator
result = func(self, *args, **kwargs)
File "/usr/local/lib/python3.5/dist-packages/telegram/bot.py", line 1264, in setWebhook
result = self._request.post(url, data, timeout=kwargs.get('timeout'))
File "/usr/local/lib/python3.5/dist-packages/telegram/utils/request.py", line 201, in post
**urlopen_kwargs)
File "/usr/local/lib/python3.5/dist-packages/telegram/utils/request.py", line 152, in _request_wrapper
raise NetworkError('{0} ({1})'.format(message, resp.status))
telegram.error.NetworkError: Too Many Requests: retry after 1 (429)
Exception in thread updater:
Traceback (most recent call last):
File "/usr/lib/python3.5/threading.py", line 914, in _bootstrap_inner
self.run()
File "/usr/lib/python3.5/threading.py", line 862, in run
self._target(*self._args, **self._kwargs)
File "/usr/local/lib/python3.5/dist-packages/telegram/ext/updater.py", line 117, in _thread_wrapper
target(*args, **kwargs)
File "/usr/local/lib/python3.5/dist-packages/telegram/ext/updater.py", line 228, in _start_polling
self._bootstrap(bootstrap_retries, clean=clean, webhook_url='')
File "/usr/local/lib/python3.5/dist-packages/telegram/ext/updater.py", line 331, in _bootstrap
self.bot.setWebhook(webhook_url=webhook_url, certificate=cert)
File "/usr/local/lib/python3.5/dist-packages/telegram/bot.py", line 126, in decorator
result = func(self, *args, **kwargs)
File "/usr/local/lib/python3.5/dist-packages/telegram/bot.py", line 1264, in setWebhook
result = self._request.post(url, data, timeout=kwargs.get('timeout'))
File "/usr/local/lib/python3.5/dist-packages/telegram/utils/request.py", line 201, in post
**urlopen_kwargs)
File "/usr/local/lib/python3.5/dist-packages/telegram/utils/request.py", line 152, in _request_wrapper
raise NetworkError('{0} ({1})'.format(message, resp.status))
telegram.error.NetworkError: Too Many Requests: retry after 1 (429)
```
### Additional information
Bot Support said:
> This kind of "Too many requests" are usually it is caused because you call setWebhook too often
Actually updater.py calls setWebhook twice:
```
if clean:
# Disable webhook for cleaning
self.bot.setWebhook(webhook_url='')
self._clean_updates()
self.bot.setWebhook(webhook_url=webhook_url, certificate=cert)
```
Maybe it's not necessary to do setWebhook when polling. Or some timeout should be set between these two calls.
