Error while pip install -r requirement.txt

[Raksha varahamurthy]

Collecting alembic==0.8.9
Downloading https://files.pythonhosted.org/packages/63/ca/c60ba17274b6737ff9ff1f89f0fbc7da93e05dd12bbdaae5099df8b60d38/alembic-0.8.9.tar.gz (977kB)
|█▍ | 40kB 37kB/s eta 0:00:25ERROR: Exception:
Traceback (most recent call last):
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/cli/base_command.py", line 153, in _main
status = self.run(options, args)
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/commands/install.py", line 382, in run
resolver.resolve(requirement_set)
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/legacy_resolve.py", line 201, in resolve
self._resolve_one(requirement_set, req)
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/legacy_resolve.py", line 365, in _resolve_one
abstract_dist = self._get_abstract_dist_for(req_to_install)
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/legacy_resolve.py", line 313, in _get_abstract_dist_for
req, self.session, self.finder, self.require_hashes
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/operations/prepare.py", line 194, in prepare_linked_requirement
progress_bar=self.progress_bar
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/download.py", line 465, in unpack_url
progress_bar=progress_bar
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/download.py", line 316, in unpack_http_url
progress_bar)
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/download.py", line 551, in _download_http_url
_download_url(resp, link, content_file, hashes, progress_bar)
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/download.py", line 253, in _download_url
hashes.check_against_chunks(downloaded_chunks)
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/utils/hashes.py", line 80, in check_against_chunks
for chunk in chunks:
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/download.py", line 223, in written_chunks
for chunk in chunks:
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/utils/ui.py", line 160, in iter
for x in it:
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_internal/download.py", line 212, in resp_read
decode_content=False):
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_vendor/urllib3/response.py", line 564, in stream
data = self.read(amt=amt, decode_content=decode_content)
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_vendor/urllib3/response.py", line 529, in read
raise IncompleteRead(self._fp_bytes_read, self.length_remaining)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/contextlib.py", line 35, in exit
self.gen.throw(type, value, traceback)
File "/Library/Python/2.7/site-packages/pip-19.3.1-py2.7.egg/pip/_vendor/urllib3/response.py", line 430, in _error_catcher
raise ReadTimeoutError(self._pool, None, "Read timed out.")
ReadTimeoutError: HTTPSConnectionPool(host='files.pythonhosted.org', port=443): Read timed out.