Collecting scrapy
Could not fetch URL https://pypi.python.org/simple/scrapy/: There was a problem confirming the ssl certificate: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:661) - skipping
Could not find a version that satisfies the requirement scrapy (from versions: )
No matching distribution found for scrapy
看起来像是公司开发网导致的无法下载，我打开了Proxifier，让它走代理服务器，解决。
再次pip install scrapy，又报错：
Collecting scrapy
Using cached https://files.pythonhosted.org/p ... y2.py3-none-any.whl
Collecting pyOpenSSL (from scrapy)
Using cached https://files.pythonhosted.org/p ... y2.py3-none-any.whl
Collecting queuelib (from scrapy)
Using cached https://files.pythonhosted.org/p ... y2.py3-none-any.whl
Collecting cssselect>=0.9 (from scrapy)
Using cached https://files.pythonhosted.org/p ... y2.py3-none-any.whl
Collecting PyDispatcher>=2.0.5 (from scrapy)
Using cached https://files.pythonhosted.org/p ... atcher-2.0.5.tar.gz
Collecting Twisted>=13.1.0 (from scrapy)
Using cached https://files.pythonhosted.org/p ... sted-17.9.0.tar.bz2
Complete output from command python setup.py egg_info:
Download error on https://pypi.python.org/simple/incremental/: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:661) -- Some packages may not be found!
Couldn't find index page for 'incremental' (maybe misspelled?)
Download error on https://pypi.python.org/simple/: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:661) -- Some packages may not be found!
No local packages or working download links found for incremental>=16.10.1
Traceback (most recent call last):
File "", line 1, in
File "/private/var/folders/c_/gmvr6xh546bcm2xtfmpc0q640000gn/T/pip-install-inDShH/Twisted/setup.py", line 21, in
setuptools.setup(**_setup["getSetupArgs"]())
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/distutils/core.py", line 111, in setup
_setup_distribution = dist = klass(attrs)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/setuptools/dist.py", line 315, in __init__
self.fetch_build_eggs(attrs['setup_requires'])
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/setuptools/dist.py", line 361, in fetch_build_eggs
replace_conflicting=True,
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pkg_resources/__init__.py", line 850, in resolve
dist = best[req.key] = env.best_match(req, ws, installer)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pkg_resources/__init__.py", line 1122, in best_match
return self.obtain(req, installer)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pkg_resources/__init__.py", line 1134, in obtain
return installer(requirement)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/setuptools/dist.py", line 429, in fetch_build_egg
return cmd.easy_install(req)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/setuptools/command/easy_install.py", line 659, in easy_install
raise DistutilsError(msg)
distutils.errors.DistutilsError: Could not find suitable distribution for Requirement.parse('incremental>=16.10.1')
----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /private/var/folders/c_/gmvr6xh546bcm2xtfmpc0q640000gn/T/pip-install-inDShH/Twisted/
从log信息中我们可以看到问题出在Collecting Twisted这一步，看Download error on https://pypi.python.org/simple/: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version 还以为是openssl的问题，然而重新安装了openssl还是报一样的错。
那么我单独安装Twisted试一下？报了一样的错
经过一番焦头烂额的搜索尝试安装了一堆我也不知道干嘛的包，还是没有解决。。
I had the same issue on a Mac OSX 10.11.6 in a new virtualenv with a fresh install of Python3.6.1. In my case, I had old versions of the Twisted dependency incremental installed, which prevented the installation.
pip install --upgrade incremental
pip install Twisted
Note I: I was installing a whole array of packages from a requirements file where the same incremental version was specified. I really wonder why the upgrade of incremental helped and have no clue what actually went wrong. If someone can clarify, that would be great.
Note II: Installing incremental ahead of of Twisted seems to be necessary on fresh installs, too [Experienced when working with CentOS7].
