oletools 0.54.2 install fails on PyPy on Windows due to cryptography missing OpenSSL

[decalage2]

When attempting to install oletools 0.54.2 on PyPy on Windows using pip, the msoffcrypto-tool package is required, which in turn requires cryptography. It looks like cryptography on PyPy (unlike on CPython) is not statically linked to OpenSSL, and it fails to install when it cannot find OpenSSL to compile it:

build\temp.win32-2.7\Release\_openssl.c(498) : fatal error C1083: Cannot open include file: 'openssl/opensslv.h': No such file or directory
error: command 'C:\\Users\\xxx\\AppDats\\Local\\Programs\\Common\\Microsoft\\Visual C++ for Python\\9.0\\VC\\Bin\\cl.exe' failed with exit status 2

Ref about cryptography install: https://cryptography.io/en/latest/installation/
Workaround:
Use oletools 0.54.1, which does not require msoffcrypto-tool, until a fix is found:
pypy -m pip install oletools==0.54.1

[decalage2]

I still get an error when installing oletools 0.56 on PyPy 2.7 on Windows: decalage2/ViperMonkey#106

The only solution seems to make msoffcrypto-tool an optional dependency, as it was the case until oletools 0.54.1.

[decalage2]

I found a way to fix this with a conditional dependency in setup.py and requirements.txt: msoffcrypto-tool will only be installed if the platform is not PyPy or not Windows (which is the same as not(PyPy and Windows)):

msoffcrypto-tool; platform_python_implementation!="PyPy" or platform_system!="Windows"

This also contributes to fixing decalage2/ViperMonkey#106