solution method:

http_proxy='http://xxx:xxx@xx.xxx.xx.x:xxx'

https_proxy='http://xxx:xxx@xx.xx.x.x:xxx'

export http_proxy

export https_proxy

reference : 

http://stackoverflow.com/questions/14149422/using-pip-behind-a-proxy

try another:

all_proxy='http://xxx:xxx@xx.xx.x.x:xxx'

when using proxy to install the package, it would output these error information below:

root@wgz:/home/wgz# pip3 install robotframework

Collecting robotframeworkException:Traceback (most recent call last):  File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connection.py", line 137, in _new_conn    (self.host, self.port), self.timeout, **extra_kw)  File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/util/connection.py", line 91, in create_connection    raise err  File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/util/connection.py", line 81, in create_connection    sock.connect(sa)OSError: [Errno 101] Network is unreachableDuring handling of the above exception, another exception occurred:Traceback (most recent call last):  File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 560, in urlopen    body=body, headers=headers)  File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 346, in _make_request    self._validate_conn(conn)  File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 787, in _validate_conn    conn.connect()  File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connection.py", line 217, in connect    conn = self._new_conn()  File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connection.py", line 146, in _new_conn    self, "Failed to establish a new connection: %s" % e)requests.packages.urllib3.exceptions.NewConnectionError:: Failed to establish a new connection: [Errno 101] Network is unreachable

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "/usr/lib/python3/dist-packages/pip/basecommand.py", line 209, in main

status = self.run(options, args)

File "/usr/lib/python3/dist-packages/pip/commands/install.py", line 328, in run

wb.build(autobuilding=True)

File "/usr/lib/python3/dist-packages/pip/wheel.py", line 748, in build

self.requirement_set.prepare_files(self.finder)

File "/usr/lib/python3/dist-packages/pip/req/req_set.py", line 360, in prepare_files

ignore_dependencies=self.ignore_dependencies))

File "/usr/lib/python3/dist-packages/pip/req/req_set.py", line 512, in _prepare_file

finder, self.upgrade, require_hashes)

File "/usr/lib/python3/dist-packages/pip/req/req_install.py", line 273, in populate_link

self.link = finder.find_requirement(self, upgrade)

File "/usr/lib/python3/dist-packages/pip/index.py", line 442, in find_requirement

all_candidates = self.find_all_candidates(req.name)

File "/usr/lib/python3/dist-packages/pip/index.py", line 400, in find_all_candidates

for page in self._get_pages(url_locations, project_name):

File "/usr/lib/python3/dist-packages/pip/index.py", line 545, in _get_pages

page = self._get_page(location)

File "/usr/lib/python3/dist-packages/pip/index.py", line 648, in _get_page

return HTMLPage.get_page(link, session=self.session)

File "/usr/lib/python3/dist-packages/pip/index.py", line 757, in get_page

"Cache-Control": "max-age=600",

File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 480, in get

return self.request('GET', url, **kwargs)

File "/usr/lib/python3/dist-packages/pip/download.py", line 378, in request

return super(PipSession, self).request(method, url, *args, **kwargs)

File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 468, in request

resp = self.send(prep, **send_kwargs)

File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 576, in send

r = adapter.send(request, **kwargs)

File "/usr/share/python-wheels/CacheControl-0.11.5-py2.py3-none-any.whl/cachecontrol/adapter.py", line 46, in send

resp = super(CacheControlAdapter, self).send(request, **kw)

File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/adapters.py", line 376, in send

timeout=timeout

File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 610, in urlopen

_stacktrace=sys.exc_info()[2])

File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/util/retry.py", line 228, in increment

total -= 1

TypeError: unsupported operand type(s) for -=: 'Retry' and 'int'