Error when uploading data

Hi to all.
I have the following errors when uploading the file with DataPusher:

Invalid HTTP response: HTTP Error 403: Forbidden

or
[u' File "/usr/lib/ckan/datapusher/lib/python2.7/site-packages/apscheduler/scheduler.py", line 512, in _run_job\n retval = job.func(_job.args, *_job.kwargs)\n',
u' File "/usr/lib/ckan/datapusher/src/datapusher/datapusher/jobs.py", line 238, in push_to_datastore\n response = urllib2.urlopen(request, timeout=DOWNLOAD_TIMEOUT)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 126, in urlopen\n return _opener.open(url, data, timeout)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 400, in open\n response = self._open(req, data)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 418, in _open\n \'_open\', req)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 378, in _call_chain\n result = func(*args)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 1207, in http_open\n return self.do_open(httplib.HTTPConnection, req)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 1177, in do_open\n raise URLError(err)\n',
u"URLError(error(111, 'Connection refused'),)"]

or
[u' File "/usr/lib/ckan/datapusher/lib/python2.7/site-packages/apscheduler/scheduler.py", line 512, in _run_job\n retval = job.func(_job.args, *_job.kwargs)\n',
u' File "/usr/lib/ckan/datapusher/src/datapusher/datapusher/jobs.py", line 238, in push_to_datastore\n response = urllib2.urlopen(request, timeout=DOWNLOAD_TIMEOUT)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 126, in urlopen\n return _opener.open(url, data, timeout)\n'
u' File "/usr/lib/python2.7/urllib2.py", line 400, in open\n response = self._open(req, data)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 418, in _open\n \'_open\', req)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 378, in _call_chain\n result = func(*args)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 1207, in http_open\n return self.do_open(httplib.HTTPConnection, req)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 1177, in do_open\n raise URLError(err)\n',
u"URLError(gaierror(-3, 'Temporary failure in name resolution'),)"]

or

[u' File "/usr/lib/ckan/datapusher/lib/python2.7/site-packages/apscheduler/scheduler.py", line 512, in _run_job\n retval = job.func(_job.args, *_job.kwargs)\n',
u' File "/usr/lib/ckan/datapusher/src/datapusher/datapusher/jobs.py", line 238, in push_to_datastore\n response = urllib2.urlopen(request, timeout=DOWNLOAD_TIMEOUT)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 126, in urlopen\n return _opener.open(url, data, timeout)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 400, in open\n response = self._open(req, data)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 418, in _open\n \'_open\', req)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 378, in _call_chain\n result = func(*args)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 1215, in https_open\n return self.do_open(httplib.HTTPSConnection, req)\n',
u' File "/usr/lib/python2.7/urllib2.py", line 1177, in do_open\n raise URLError(err)\n', u"URLError(error(101, 'Network is unreachable'),)"]

it seems to me that the problem is because the server is running behind a proxy.

And perhaps, the opener is not correctly setted, by getting the proxy options from the system, i.e.:
proxy = urllib2.ProxyHandler()
opener = urllib2.build_opener(proxy)