util: move get_host_storage() to a separate module

Add a new util module called host which is used for functions that are
meant for interactions with the host.  These functions should not be
used in stages.

The containers.get_host_storage() function is renamed to
host.get_container_storage() for clarity, since it is no longer
namespaced under containers.

inputs/org.osbuild.containers-storage

@@ -15,7 +15,7 @@ import os
 import sys
 
 from osbuild import inputs
-from osbuild.util import containers
+from osbuild.util import host
 from osbuild.util.mnt import MountGuard
 
 SCHEMA = r"""
@@ -89,7 +89,7 @@ class ContainersStorageInput(inputs.InputService):
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.mg = MountGuard()
-        self.storage_conf = containers.get_host_storage()
+        self.storage_conf = host.get_container_storage()
 
     def bind_mount_local_storage(self, target):
         source = self.storage_conf["storage"]["graphroot"]

osbuild/util/containers.py

@@ -180,21 +180,3 @@ def container_source(image):
 
     with container_source_fn(image, image_filepath, container_format) as image_source:
         yield image_name, image_source
-
-
-def get_host_storage():
-    """
-    Read the host storage configuration.
-    """
-    # pylint: disable=import-outside-toplevel
-    # importing this at the top level will break the buildroot
-    from osbuild.util import toml
-
-    config_paths = ("/etc/containers/storage.conf", "/usr/share/containers/storage.conf")
-    for conf_path in config_paths:
-        try:
-            return toml.load_from_file(conf_path)
-        except FileNotFoundError:
-            pass
-
-    raise FileNotFoundError(f"could not find container storage configuration in any of {config_paths}")

osbuild/util/host.py

@@ -0,0 +1,20 @@
+"""
+Utility functions that only run on the host (osbuild internals or host modules like sources).
+
+These should not be used by stages or code that runs in the build root.
+"""
+from osbuild.util import toml
+
+
+def get_container_storage():
+    """
+    Read the host storage configuration.
+    """
+    config_paths = ("/etc/containers/storage.conf", "/usr/share/containers/storage.conf")
+    for conf_path in config_paths:
+        try:
+            return toml.load_from_file(conf_path)
+        except FileNotFoundError:
+            pass
+
+    raise FileNotFoundError(f"could not find container storage configuration in any of {config_paths}")

sources/org.osbuild.containers-storage

@@ -18,7 +18,7 @@ import subprocess as sp
 import sys
 
 from osbuild import sources
-from osbuild.util import containers
+from osbuild.util import host
 
 SCHEMA = """
 "additionalProperties": false,
@@ -49,7 +49,7 @@ class ContainersStorageSource(sources.SourceService):
         Construct the full image name that references an image with a given checksum in the local storage.
         """
         if self.storage_conf is None:
-            conf = containers.get_host_storage()
+            conf = host.get_container_storage()
         driver = conf["storage"]["driver"]
         graphroot = conf["storage"]["graphroot"]
         runroot = conf["storage"]["runroot"]