virt-install 1:1.5.1-0 passing url of iso file results in unexpected error

[Simon Kobyda]

When you try to pass url of iso file as --disk parameter, error is returned:

if you pass nonexistent url: Error validating install location: Could not find an installable distribution at 'http://foo.com/image.iso': The URL could not be accessed, maybe you mistyped
if you pass valid and existing url: ERROR Error validating install location: Could not find an installable distribution at ...

Proper behavior: XML is expected to be printed out.

How to reproduce:
$ virt-install --name bla --memory 10 --cdrom http://foo.com/file.iso --dry-run --print-xml --disk none

Version where bug is present: v1.5.0

Version where bug is fixes: v2.0.0

Commit which fixes bug: b90b8e3c07b97125486430854aee664c73b3dea2

[Christian Ehrhardt  (paelzer)]

Fixed in >=Disco due to virt-manager 2.0 being present there.

[Christian Ehrhardt  (paelzer)]

Reading the discussion [1] and the commit [2] I see a problem with SRUing this without some more tests.

Formerly passing an URL to CDROM was meant to fetch $URL/boot.iso and use that
New: passing an URL to CDROM will mean pass $URL to qemu to open from http

That is no SRU compatible change unless passing an URL never worked in any way.
You reported that "if you pass valid and existing url: ERROR Error validating ..."
I'd need to check if that is true in "any" cases.

Only a few distros have a matching directory structure and that also is the reason the feature was removed/changed. But as of today this works fine:
$ virt-install --name bla --memory 10 --cdrom http://mirrors.mit.edu/centos/7/os/x86_64/ --dry-run --print-xml --disk none
<domain type="kvm">
  <name>bla</name>
...

And SRUing this change would thereby break some valid existing use-cases.
Due to that Nack to backporting the change.

[1]: https://www.redhat.com/archives/virt-tools-list/2018-May/msg00011.html
[2]: https://github.com/virt-manager/virt-manager/commit/b90b8e3c07b97125486430854aee664c73b3dea2