cryptography AssertionError: sorry, but this version only supports 100 named groups
<p>I'm installing several python packages via <code>pip install</code> on travis, </p>

<pre><code>language: python
python:
- '2.7'
install:
- pip install -r requirements/env.txt
</code></pre>

<p>Everything worked fine, but today I started getting following error:</p>

<pre><code> Running setup.py install for cryptography
Traceback (most recent call last):
  File "&lt;string&gt;", line 1, in &lt;module&gt;
  File "/tmp/pip-build-hKwMR3/cryptography/setup.py", line 334, in &lt;module&gt;
    **keywords_with_side_effects(sys.argv)
  File "/opt/python/2.7.9/lib/python2.7/distutils/core.py", line 111, in setup
    _setup_distribution = dist = klass(attrs)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/setuptools/dist.py", line 269, in __init__
    _Distribution.__init__(self,attrs)
  File "/opt/python/2.7.9/lib/python2.7/distutils/dist.py", line 287, in __init__
    self.finalize_options()
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/setuptools/dist.py", line 325, in finalize_options
    ep.load()(self, ep.name, value)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/cffi/setuptools_ext.py", line 181, in cffi_modules
    add_cffi_module(dist, cffi_module)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/cffi/setuptools_ext.py", line 48, in add_cffi_module
    execfile(build_file_name, mod_vars)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/cffi/setuptools_ext.py", line 24, in execfile
    exec(code, glob, glob)
  File "src/_cffi_src/build_openssl.py", line 81, in &lt;module&gt;
    extra_link_args=extra_link_args(compiler_type()),
  File "/tmp/pip-build-hKwMR3/cryptography/src/_cffi_src/utils.py", line 61, in build_ffi_for_binding
    extra_link_args=extra_link_args,
  File "/tmp/pip-build-hKwMR3/cryptography/src/_cffi_src/utils.py", line 70, in build_ffi
    ffi.cdef(cdef_source)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/cffi/api.py", line 105, in cdef
    self._cdef(csource, override=override, packed=packed)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/cffi/api.py", line 119, in _cdef
    self._parser.parse(csource, override=override, **options)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/cffi/cparser.py", line 299, in parse
    self._internal_parse(csource)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/cffi/cparser.py", line 304, in _internal_parse
    ast, macros, csource = self._parse(csource)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/cffi/cparser.py", line 260, in _parse
    ast = _get_parser().parse(csource)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/cffi/cparser.py", line 40, in _get_parser
    _parser_cache = pycparser.CParser()
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/pycparser/c_parser.py", line 87, in __init__
    outputdir=taboutputdir)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/pycparser/c_lexer.py", line 66, in build
    self.lexer = lex.lex(object=self, **kwargs)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/pycparser/ply/lex.py", line 911, in lex
    lexobj.readtab(lextab, ldict)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/site-packages/pycparser/ply/lex.py", line 233, in readtab
    titem.append((re.compile(pat, lextab._lexreflags | re.VERBOSE), _names_to_funcs(func_name, fdict)))
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/re.py", line 194, in compile
    return _compile(pattern, flags)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/re.py", line 249, in _compile
    p = sre_compile.compile(pattern, flags)
  File "/home/travis/virtualenv/python2.7.9/lib/python2.7/sre_compile.py", line 583, in compile
    "sorry, but this version only supports 100 named groups"
AssertionError: sorry, but this version only supports 100 named groups
</code></pre>

<p>Solutions?</p>

<p>There is a bug with PyCParser - See <a href="https://github.com/pyca/cryptography/issues/3187">https://github.com/pyca/cryptography/issues/3187</a></p>

<p>The work around is to use another version or to not use the binary distribution.</p>

<pre><code>pip install git+https://github.com/eliben/pycparser@release_v2.14
</code></pre>

<p>or</p>

<pre><code>pip install --no-binary pycparser
</code></pre>

python python-2.7 travis-ci python-cryptography