tools/osbuild-depsolve-dnf(5): use url.path to drop scheme

str.removeprefix() is not available in Python 3.6, which we need to
support EL8.

Instead of removing the prefix from the original path string, take the
path property of the parsed URL.  Since we're dealing with file paths,
there will be no params, query, or fragment strings so the path should
be all we need.

tools/osbuild-depsolve-dnf

@@ -326,7 +326,7 @@ def read_keys(paths, root_dir=None):
     for path in paths:
         url = urllib.parse.urlparse(path)
         if url.scheme == "file":
-            path = path.removeprefix("file://")
+            path = url.path
             path = modify_rootdir_path(path, root_dir)
             try:
                 with open(path, mode="r", encoding="utf-8") as keyfile:

tools/osbuild-depsolve-dnf5

@@ -468,7 +468,7 @@ def read_keys(paths, root_dir=None):
     for path in paths:
         url = urllib.parse.urlparse(path)
         if url.scheme == "file":
-            path = path.removeprefix("file://")
+            path = url.path
             path = modify_rootdir_path(path, root_dir)
             try:
                 with open(path, mode="r", encoding="utf-8") as keyfile: