The 2nd paragraph in section 16.2 (Reading Text Files) reads:

"The $href argument must be a string in the form of a URI. The URI must contain no fragment identifier, and must identify a resource that can be read as text. If the URI is a relative URI, then it is resolved relative to the base URI from the static context."

What is the error code if the URI contains a fragment identifier? 

This section of the spec contains the following 3 error codes which I believe do not apply:

[ERR XTDE1170] It is a non-recoverable dynamic error if a URI cannot be used to retrieve a resource containing text.
[ERR XTDE1190] It is a non-recoverable dynamic error if a resource contains octets that cannot be decoded into Unicode characters ...
[ERR XTDE1200] It is a non-recoverable dynamic error if the second argument of the unparsed-text function is omitted and the processor cannot infer the encoding ..