python - Installing via `setup.py develop` fails - pip works -

my python package footools needs html5lib via install_requires in setup.py.

setup.py develop fails

installing via setup.py develop fails:

cd src/footools/ python setup.py develop  processing dependencies footools==2016.205 searching html5lib==0.9999999 reading https://source.example.com/pypi/simple/html5lib/ download error on https://source.example.com/pypi/simple/html5lib/:     [errno 185090050] _ssl.c:354: error:0b084002:x509     certificate routines:x509_load_cert_crl_file:system lib --     packages may not found! couldn't find index page 'html5lib' (maybe misspelled?) 

pip works

but direct download works:

bar@workdevel123:~/src/footools> pip install html5lib==0.9999999 /home/bar/lib/python2.7/site-packages/pip/_vendor/requests/packages/urllib3/util/ssl_.py:79:  insecureplatformwarning: true sslcontext object not available.  prevents urllib3 configuring ssl appropriately , may cause ssl connections fail.  more information, see  https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.   insecureplatformwarning collecting html5lib==0.9999999 /home/bar/lib/python2.7/site-packages/pip/_vendor/requests/packages/urllib3/util/ssl_.py:79:      insecureplatformwarning: true sslcontext object not available.      prevents urllib3 configuring ssl appropriately ,     may cause ssl connections fail.      more information,     see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.   insecureplatformwarning   downloading https://source.example.com/pypi/packages/html5lib-0.9999999.tar.gz requirement satisfied (use --upgrade upgrade): 6 in /usr/lib/python2.7/site-packages (from html5lib==0.9999999) installing collected packages: html5lib   running setup.py install html5lib installed html5lib-0.9999999 

questions

what difference between these 2 methods?

why different?

what correct way install dependency in python?

setup.py

the setup.py not special:

import setuptools  setuptools.setup(     name='foo',     version='2016.210',     long_description=open('readme.txt').read(),     packages=setuptools.find_packages(),     install_requires=[         # twenty packages before line         'html5lib==0.9999999' ],     include_package_data=true,     entry_points={         'console_scripts': [             'foo=foo.utils.bar:main',         ],     }, ) 

python setup.py develop, or setuptools in general uses easy_install satisfy dependencies in turn uses urllib2 whereas pip uses requests. see here easy_install vs pip.
pip more modern , among other things has capability uninstall packages , complies pep 438 -- transitioning release-file hosting on pypi. can achieve same thing python setup.py develop pip install -e src/footools/, note if project path in current directory use, ./footools.

the requests package bundles ca certs in package itself, python -c 'import pip;print(pip.download.requests.certs.where())'.

setuptools uses system installed ca certs python -c 'from setuptools import ssl_support;print(ssl_support.cert_paths)'.

you have update system installed ca certs using tools update-ca-certificates ubuntu either update ca certs automatically or download https://curl.haxx.se/docs/caextract.html , install 1 of paths shown setuptools or set setuptools.ssl_support.cert_paths empy sequence [] , pip install certifi. calling setuptools.ssl_support.find_ca_bundle() reveal location of ca certs.