Fix pylint issue E0606: possibly-used-before-assignment

Fix:
assemblers/org.osbuild.qemu:310:36: E0606: Possibly using variable 'prep_type' before assignment (possibly-used-before-assignment)
inputs/org.osbuild.tree:85:15: E0606: Possibly using variable 'path' before assignment (possibly-used-before-assignment)
stages/org.osbuild.sfdisk:58:36: E0606: Possibly using variable 'prep_type' before assignment (possibly-used-before-assignment)
stages/org.osbuild.systemd.unit:23:16: E0606: Possibly using variable 'unit_dropins_dir' before assignment (possibly-used-before-assignment)
test/mod/test_meta.py:219:29: E0606: Possibly using variable 'schema_part' before assignment (possibly-used-before-assignment)

Signed-off-by: Tomáš Hozza <thozza@redhat.com>

assemblers/org.osbuild.qemu

@@ -305,6 +305,8 @@ class PartitionTable:
             prep_type = "41"
         elif self.label == "gpt":
             prep_type = "9E1A2D38-C612-4316-AA26-8B49521E5A8B"
+        else:
+            raise RuntimeError(f"Unknown partition table type: {self.label}")
 
         for part in self.partitions:
             if part.type.upper() == prep_type:

inputs/org.osbuild.tree

@@ -79,6 +79,7 @@ class TreeInput(inputs.InputService):
         # and we have exactly one reference, i.e. a pipeline id
         pid, _ = refs.popitem()
 
+        path = None
         if pid:
             path = store.read_tree_at(pid, target)
 

stages/org.osbuild.sfdisk

@@ -53,6 +53,8 @@ class PartitionTable:
             prep_type = "41"
         elif self.label == "gpt":
             prep_type = "9E1A2D38-C612-4316-AA26-8B49521E5A8B"
+        else:
+            raise RuntimeError(f"Unknown partition table type: {self.label}")
 
         for part in self.partitions:
             if part.type.upper() == prep_type:

stages/org.osbuild.systemd.unit

@@ -20,6 +20,10 @@ def main(tree, options):
         unit_dropins_dir = f"{tree}/usr/lib/systemd/system/{unit}.d"
     elif unit_type == "global":
         unit_dropins_dir = f"{tree}/usr/lib/systemd/user/{unit}.d"
+    else:
+        print(f"Error: Unknown unit type: {unit_type}")
+        return 1
+
     os.makedirs(unit_dropins_dir, exist_ok=True)
 
     # We trick configparser into letting us write multiple instances of the same option by writing them as keys with no

test/mod/test_meta.py

@@ -206,6 +206,7 @@ def make_fake_meta_json(tmp_path, name, version, invalid=""):
         "not": "following schema"
         """
 
+    # pylint: disable=possibly-used-before-assignment
     meta_json_path.write_text("""
     {
       "summary": "some json summary",