Narrow Python Build

最近线上遇到了一个问题，是在访问 https://feed.awesound.com/pysva 这个URL时候出现的。重现过程非常简单

In [25]: url = 'https://feed.awesound.com/pysva'

In [26]: r = requests.get(url)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-26-0aec23ab0de0> in <module>()
----> 1 r = requests.get(url)

...

/usr/local/Cellar/python/2.7.10_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/requests/packages/urllib3/contrib/pyopenssl.pyc in get_subj_alt_name(peer_cert)
    191     # faster than looping in Python)
    192     try:
--> 193         ext = cert.extensions.get_extension_for_class(
    194             x509.SubjectAlternativeName
    195         ).value

/usr/local/Cellar/python/2.7.10_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/cryptography/hazmat/backends/openssl/x509.pyc in extensions(self)
    128     @property
    129     def extensions(self):
--> 130         return _CERTIFICATE_EXTENSION_PARSER.parse(self._backend, self._x509)
    131
    132     @property

...

/usr/local/Cellar/python/2.7.10_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings/punycode.pyc in insertion_sort(base, extended, errors)
    178             char = ord('?')
    179         pos = pos % (len(base) + 1)
--> 180         base = base[:pos] + unichr(char) + base[pos:]
    181         bias = adapt(delta, (extpos == 0), len(base))
    182         extpos = newpos

ValueError: unichr() arg not in range(0x10000) (narrow Python build)

在很长一段时间内没有遇到过这个问题。什么叫做 "narrow python build" , 就是使用两个字节来存储一个unicode字符。从 stacktrace 上来看，这个问题是处在解析SSL证书的时候出现的。

至于如何来解决这个 "narrow python build" 问题，可以看 这篇 文章(没有什么好的解决办法，两个办法的成本都非常高，一个是重新编译Python2, 一个是切换到Python3)

为了更加确定是SSL证书的问题，我们可以访问http站点，实验证明的确是这样。

In [27]: r = requests.get(url.replace('https://', 'http://'))

In [28]: r
Out[28]: <Response [200]>