def add_header(message, name, val):
# Must bypass Django's SafeMIMEMessage.__set_item__, because its call to
# forbid_multi_line_headers converts the val back to a str, undoing this
# workaround. That makes this code responsible for sanitizing val:
if '\n' in val or '\r' in val:
raise BadHeaderError("Header values can't contain newlines (got %r for header %r)" % (val, name))
val = HeaderBugWorkaround(val, header_name=name)
assert isinstance(message, MIMEBase)
MIMEBase.__setitem__(message, name, val)
