Comment 5 for bug 1911928

I did some more analysis, and in some situations this may work, however, the following scenario always fails

1-types.xsd includes the entities.dtd
1-main.xsd defines elements that use types defined in 1-types.xsd
1.xml instantiates the element from 1-main.xsd

entities.dtd
<!ENTITY digit "0-9">
<!ENTITY uword "([&digit;]{1,4}|[1-5][&digit;]{4}|6[0-4][&digit;]{3}|65[0-4][&digit;]{2}|655[0-2][&digit;]|6553[0-5])">
<!ENTITY Port ":&uword;">

1-types.xsd
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE schema SYSTEM "entities.dtd">
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="urn:paul:types1" targetNamespace="urn:paul:types1" elementFormDefault="qualified" attributeFormDefault="unqualified">
 <xs:simpleType name="PortType">
  <xs:restriction base="xs:string">
   <xs:pattern value="&Port;"/>
  </xs:restriction>
 </xs:simpleType>
</xs:schema>

1-main.xsd
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE schema SYSTEM "entities.dtd">
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="urn:paul:main1" xmlns:t="urn:paul:types1" targetNamespace="urn:paul:main1" elementFormDefault="qualified" attributeFormDefault="unqualified">
 <xs:import namespace="urn:paul:types1" schemaLocation="1-types.xsd"/>
 <xs:element name="Port" type="t:PortType"/>
</xs:schema>

1.xml
<?xml version="1.0" encoding="UTF-8"?>
<Port xmlns="urn:paul:main1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:paul:main1 1-main.xsd">:101001</Port>

test1.py
import lxml
from lxml import etree

myParser = lxml.etree.XMLParser()

with open('1-types.xsd', 'r') as baseschema_file:
    baseschema=etree.parse(baseschema_file, parser=myParser)
    baseschema.xinclude()
    my_baseschema=etree.XMLSchema(baseschema)

with open('1-main.xsd', 'r') as schema_file:
    mainschema=etree.parse(schema_file, parser=myParser)
    my_schema=etree.XMLSchema(mainschema)

with open('1.xml') as file:
    my_xml=etree.parse(file)
    my_schema.assertValid(my_xml)

==> error
Traceback (most recent call last):
  File "G:\lxml-test\test1.py", line 18, in <module>
    my_schema.assertValid(my_xml)
  File "src\lxml\etree.pyx", line 3623, in lxml.etree._Validator.assertValid
lxml.etree.DocumentInvalid: Element '{urn:paul:main1}Port': [facet 'pattern'] The value ':101001' is not accepted by the pattern ''., line 2