We expect the special characters to be compliant with RFC3986.
Supported characters are:
a-z, A-Z, 0-9
-_ % ! $ & ' ( ) * + , ; =
Unsupported characters are:
:/?#[]@
The regular expression using pythonic dialect of regexp: ^[a-zA-Z0-9_.\-~%!$&\'()*+,;=]*{0,64}$