update to python3.7

lib/python3.7/site-packages/asn1crypto/_ffi.py

@@ -0,0 +1,45 @@
+# coding: utf-8
+
+"""
+FFI helper compatibility functions. Exports the following items:
+
+ - LibraryNotFoundError
+ - FFIEngineError
+ - bytes_from_buffer()
+ - buffer_from_bytes()
+ - null()
+"""
+
+from __future__ import unicode_literals, division, absolute_import, print_function
+
+from ctypes import create_string_buffer
+
+
+def buffer_from_bytes(initializer):
+    return create_string_buffer(initializer)
+
+
+def bytes_from_buffer(buffer, maxlen=None):
+    return buffer.raw
+
+
+def null():
+    return None
+
+
+class LibraryNotFoundError(Exception):
+
+    """
+    An exception when trying to find a shared library
+    """
+
+    pass
+
+
+class FFIEngineError(Exception):
+
+    """
+    An exception when trying to instantiate ctypes or cffi
+    """
+
+    pass