we have an xml document which has a dtd hosted at an https url. xmllint cannot pull the dtd and complains.

$ xmllint test.xml --noout --valid
test.xml:2: I/O error : failed to load external entity "https://host.example.com/dtd/test.dtd"
YPE test SYSTEM "https://host.example.com/dtd/test.dtd"
                                                      ^
test.xml:2: warning: failed to load external entity "https://host.example.com/dtd/test.dtd"
YPE test SYSTEM "https://host.example.com/dtd/test.dtd"
                                                      ^
test.xml:3: validity error : Validation failed: no DTD found !
<test version="4">
                 ^

please update nanohttp (which xmllint uses to fetch the dtd) to support https, or have some way to build xmllint with libcurl.

thanks.