urldetect: Use libosinfo for tree detection too

Ask libosinfo for tree detection, but still fall back to our
own implementation if libosinfo fails

tests/test_urls.ini

@@ -57,11 +57,11 @@ distro = centos6.10
 # Latest scientific 6, detected as centos
 [centos-sl6-latest]
 url = http://ftp.scientificlinux.org/linux/scientific/6/x86_64/os
-distro = centos6.10
+distro = scientificlinux6.10
 # Latest scientific 7, detected as centos
 [centos-sl7-latest]
 url = http://ftp.scientificlinux.org/linux/scientific/7/x86_64/os
-distro = centos7.0
+distro = scientificlinux7.6
 
 # centos7 with exotic archs (i686 is dead)
 [centos-7-latest]

virtinst/osdict.py

@@ -229,6 +229,20 @@ class _OSDB(object):
             return None
         return media.get_os().get_short_id(), media
 
+    def guess_os_by_tree(self, location):
+        if location.startswith("/"):
+            location = "file://" + location
+        try:
+            tree = Libosinfo.Tree.create_from_location(location, None)
+        except Exception as e:
+            logging.debug("Error creating libosinfo tree object: %s", str(e))
+            return None
+
+        osobj, treeobj = self._os_loader.get_db().guess_os_from_tree(tree)
+        if not osobj:
+            return None
+        return osobj.get_short_id(), treeobj
+
     def list_os(self):
         """
         List all OSes in the DB

virtinst/urldetect.py

@@ -162,7 +162,14 @@ class _DistroCache(object):
                           "path for detected os_variant=%s",
                           self.libosinfo_mediaobj)
             return False
+        return True
 
+    def guess_os_from_tree(self):
+        ret = OSDB.guess_os_by_tree(self._fetcher.location)
+        if not ret:
+            return False
+        self.libosinfo_os_variant = ret[0]
+        self.treeinfo_matched = True
         return True
 
 
@@ -821,7 +828,7 @@ class _LibosinfoDistro(_DistroTree):
     def is_valid(cls, cache):
         if cache.fetcher_is_iso():
             return cache.guess_os_from_iso()
-        return False
+        return cache.guess_os_from_tree()
 
     def _set_manual_kernel_paths(self):
         self._kernel_paths += [