我尝试通过以下方式安装Cryptography：
lsn@lsn-Super-Server:~/pypy/pypy3-v6.0.0-linux64/bin$ ./pypy3 -m pip install PyMySQL
但是，它的评论失败了：
running egg_info
writing src/cryptography.egg-info/PKG-INFO
writing dependency_links to src/cryptography.egg-info/dependency_links.txt
writing requirements to src/cryptography.egg-info/requires.txt
writing top-level names to src/cryptography.egg-info/top_level.txt
reading manifest file 'src/cryptography.egg-info/SOURCES.txt'
reading manifest template 'MANIFEST.in'
no previously-included directories found matching 'docs/_build'
warning: no previously-included files matching '*' found under directory 'vectors'
writing manifest file 'src/cryptography.egg-info/SOURCES.txt'
running build_ext
generating cffi module 'build/temp.linux-x86_64-3.5/_padding.c'
creating build/temp.linux-x86_64-3.5
generating cffi module 'build/temp.linux-x86_64-3.5/_constant_time.c'
generating cffi module 'build/temp.linux-x86_64-3.5/_openssl.c'
building '_openssl' extension
creating build/temp.linux-x86_64-3.5/build
creating build/temp.linux-x86_64-3.5/build/temp.linux-x86_64-3.5
cc -pthread -DNDEBUG -O2 -Qunused-arguments -fPIC -I/home/lsn/pypy/pypy3-v6.0.0-linux64/include -c build/temp.linux-x86_64-3.5/_openssl.c -o build/temp.linux-x86_64-3.5/build/temp.linux-x86_64-3.5/_openssl.o -Wconversion -Wno-error=sign-conversion
cc: error: unrecognized command line option ‘-Qunused-arguments’; did you mean ‘-Wunused-parameter’?
error: command 'cc' failed with exit status 1
----------------------------------------
Command "/home/lsn/pypy/pypy3-v6.0.0-linux64/bin/pypy3 -u -c "import setuptools, tokenize;__file__='/tmp/pip-install-87db0m7x/Cryptography/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /tmp/pip-record-9zd03ixf/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /tmp/pip-install-87db0m7x/Cryptography/
我在为python3安装paypalrestsdk时遇到了同样的错误，我找到了需要安装或更新python-openssl的解决方案。
尝试下面的命令，它对我有用。
对于python2
sudo apt-get install python-openssl
对于python3
sudo apt-get install python3-openssl
希望它也适合你。