>>> import io
>>> from mechanize import _opener, HTTPError

Normal case.  Response goes through hook function and is returned.

>>> def urlopen(fullurl, data=None, timeout=None):
...     print("fullurl %r" % fullurl)
...     print("data %r" % data)
...     return "response"
>>> def response_hook(response):
...     print("response %r" % response)
...     return "processed response"
>>> _opener.wrapped_open(urlopen, response_hook,
...                      "http://example.com", "data"
...                      )
fullurl 'http://example.com'
data 'data'
response 'response'
'processed response'


Raised HTTPError exceptions still go through the response hook but
the result is raised rather than returned.

>>> def urlopen(fullurl, data=None, timeout=None):
...     print("fullurl %r" % fullurl)
...     print("data %r" % data)
...     raise HTTPError(
...         "http://example.com", 200, "OK", {}, io.BytesIO())
>>> def response_hook(response):
...     print("response class %s" % response.__class__.__name__)
...     return Exception("processed response")
>>> try:
...     _opener.wrapped_open(urlopen, response_hook,
...                          "http://example.com", "data"
...                          )
... except Exception as exc:
...     print(exc)
fullurl 'http://example.com'
data 'data'
response class HTTPError
processed response

Other exceptions get ignored, since they're not response objects.

>>> def urlopen(fullurl, data=None, timeout=None):
...     print("fullurl %r" % fullurl)
...     print("data %r" % data)
...     raise Exception("not caught")
>>> try:
...     _opener.wrapped_open(urlopen, response_hook,
...                          "http://example.com", "data"
...                          )
... except Exception as exc:
...     print(exc)
fullurl 'http://example.com'
data 'data'
not caught
