Update requests to 2.18.4

lib/requests/_internal_utils.py

@@ -0,0 +1,42 @@
+# -*- coding: utf-8 -*-
+
+"""
+requests._internal_utils
+~~~~~~~~~~~~~~
+
+Provides utility functions that are consumed internally by Requests
+which depend on extremely few external helpers (such as compat)
+"""
+
+from .compat import is_py2, builtin_str, str
+
+
+def to_native_string(string, encoding='ascii'):
+    """Given a string object, regardless of type, returns a representation of
+    that string in the native string type, encoding and decoding where
+    necessary. This assumes ASCII unless told otherwise.
+    """
+    if isinstance(string, builtin_str):
+        out = string
+    else:
+        if is_py2:
+            out = string.encode(encoding)
+        else:
+            out = string.decode(encoding)
+
+    return out
+
+
+def unicode_is_ascii(u_string):
+    """Determine if unicode string only contains ASCII characters.
+
+    :param str u_string: unicode string to check. Must be unicode
+        and not Python 2 `str`.
+    :rtype: bool
+    """
+    assert isinstance(u_string, str)
+    try:
+        u_string.encode('ascii')
+        return True
+    except UnicodeEncodeError:
+        return False