Failed: pip install -r requirements.txt - can't parse python_version clause
<p>I'm trying to install SAIO as <a href="http://docs.openstack.org/developer/swift/development_saio.html#common-dev-section" rel="nofollow">http://docs.openstack.org/developer/swift/development_saio.html#common-dev-section</a></p>

<p>when I nuild a development installation of swift by</p>

<pre><code>pip install -r requirements.txt
</code></pre>

<p>I got this error:</p>

<pre><code>Exception:
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 122, in main
    status = self.run(options, args)
  File "/usr/lib/python2.7/dist-packages/pip/commands/install.py", line 262, in run
    for req in parse_requirements(filename, finder=finder, options=options, session=session):
  File "/usr/lib/python2.7/dist-packages/pip/req.py", line 1632, in parse_requirements
    req = InstallRequirement.from_line(line, comes_from, prereleases=getattr(options, "pre", None))
  File "/usr/lib/python2.7/dist-packages/pip/req.py", line 173, in from_line
    return cls(req, comes_from, url=url, prereleases=prereleases)
  File "/usr/lib/python2.7/dist-packages/pip/req.py", line 71, in __init__
    req = pkg_resources.Requirement.parse(req)
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2667, in parse
    reqs = list(parse_requirements(s))
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2605, in parse_requirements
    line, p, specs = scan_list(VERSION,LINE_END,line,p,(1,2),"version spec")
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2583, in scan_list
    "Expected ',' or end-of-list in",line,"at",line[p:]
ValueError: ("Expected ',' or end-of-list in", "dnspython3&gt;=1.12.0;python_version&lt;'3.0'", 'at', ";python_version&lt;'3.0'")

Storing debug log for failure in /root/.pip/pip.log
</code></pre>

<p>here is my requirement.txt</p>

<pre><code>dnspython3&gt;=1.12.0;python_version&lt;'3.0'
dnspython3&gt;=1.12.0;python_version&gt;='3.0'
eventlet&gt;=0.17.4  # MIT
greenlet&gt;=0.3.1
netifaces&gt;=0.5,!=0.10.0,!=0.10.1
pastedeploy&gt;=1.3.3
six&gt;=1.9.0
xattr&gt;=0.4
PyECLib&gt;=1.2.0                          # BSD
</code></pre>