Need method of recovery when a proxy error occurs downloading streamgage data

[pnorton-usgs]

When a proxy error occurs while downloading streamgage data the program crashes (see output example below). Should add logic to attempt recovery when this happens and provide a better error message when the program must exit.

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Generating stream network from tosegment_nhm
Extracting model subset
Parameter file written: /cxfs/projects/usgs/water/mows/NHM/bandit/jobs/20170620_GCPO/myparam.param
Processing CBH files
Downloading NWIS streamgage observations for 1235 stations
Streamgage: 08073500 (6/1235) ERROR: More than one Q-col returned
Streamgage: 08075000 (22/1235) Traceback (most recent call last):
File "../../Bandit/bandit.py", line 581, in
main()
File "../../Bandit/bandit.py", line 548, in main
streamflow.get_daily_streamgage_observations()
File "/cxfs/projects/usgs/water/mows/NHM/bandit/Bandit/prms_nwis.py", line 153, in get_daily_streamgage_observations
streamgage_obs_page = urlopen('{}/dv/{}'.format(BASE_NWIS_URL, url_final))
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 154, in urlopen
return opener.open(url, data, timeout)
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 435, in open
response = meth(req, response)
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 548, in http_response
'http', request, response, code, msg, hdrs)
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 467, in error
result = self._call_chain(*args)
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 407, in _call_chain
result = func(*args)
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 654, in http_error_302
return self.parent.open(new, timeout=req.timeout)
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 435, in open
response = meth(req, response)
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 548, in http_response
'http', request, response, code, msg, hdrs)
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 473, in error
return self._call_chain(*args)
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 407, in _call_chain
result = func(*args)
File "/home/pnorton/.conda/envs/bandit/lib/python2.7/urllib2.py", line 556, in http_error_default
raise HTTPError(req.get_full_url(), code, msg, hdrs, fp)
urllib2.HTTPError: HTTP Error 502: Proxy Error