Require py3 for msoffcrypto

Quoting the deprecation warning for encryption, which is needed for
msoffcrypto:

Python 2 is no longer supported by the Python core team. Support for it is
now deprecated in cryptography, and will be removed in the next release.

requirements.txt

@@ -2,5 +2,5 @@ pyparsing>=2.1.0,<3
 olefile>=0.46
 easygui
 colorclass
-msoffcrypto-tool; platform_python_implementation!="PyPy" or (python_version>="3" and platform_system!="Windows" and platform_system!="Darwin")
+msoffcrypto-tool; python_version>="3" and (platform_python_implementation!="PyPy" or platform_system!="Windows" and platform_system!="Darwin")
 pcodedmp>=1.2.5

setup.py

@@ -325,8 +325,10 @@ def main():
             "easygui",
             'colorclass',
             # msoffcrypto-tool is not installable on PyPy+Windows (see issue #473),
-            # so we only require it if the platform is not Windows or not PyPy:
-            'msoffcrypto-tool; platform_python_implementation!="PyPy" or (python_version>="3" and platform_system!="Windows" and platform_system!="Darwin")',
+            # so we only require it if the platform is not Windows or not PyPy;
+            # Also, usage of cryptography (used by msoffcrypt-tool) is deprecated for py2
+            'msoffcrypto-tool; (python_version>="3" and platform_python_implementation!="PyPy") \
+                or (python_version>="3" and platform_system!="Windows" and platform_system!="Darwin")',
             'pcodedmp>=1.2.5',
         ],
         extras_require={