Disable value interpolation in configparser

The metadata is a text file and cannot use $ or %. A % can occur in
uri value of Extra Data which can't be parsed with interpolation
enabled

flatpak_builder_lint/builddir.py

@@ -21,7 +21,7 @@ def get_metadata(builddir: str) -> dict:
 
 
 def parse_metadata(ini: str) -> dict:
-    parser = ConfigParser()
+    parser = ConfigParser(interpolation=None)
     parser.optionxform = str  # type: ignore
     parser.read_string(ini)
 

tests/builddir/metadata-spaces/metadata

@@ -0,0 +1,17 @@
+[Application]
+name=org.flathub.example-spaces
+command=example spaces
+
+[Context]
+persistent=.foo bar
+filesystems=~/foo bar
+
+[Extra Data]
+name=example spaces.ext
+checksum=b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c
+size=1
+uri=https://example.org/foo%20bar.ext
+name1=example%20spaces.ext
+checksum1=1f2ec52b774368781bed1d1fb140a92e0eb6348090619c9291f9a5a3c8e8d151
+size1=1
+uri1=https://example.org/foo bar.ext

tests/test_builddir.py

@@ -98,3 +98,15 @@ def test_builddir_console() -> None:
     found_errors = set(ret["errors"])
 
     assert errors == found_errors
+
+def test_builddir_metadata_spaces() -> None:
+    errors = {
+        "appstream-metainfo-missing",
+        "appstream-missing-icon-file",
+        "appstream-missing-appinfo-file"
+    }
+
+    ret = run_checks("tests/builddir/metadata-spaces")
+    found_errors = set(ret["errors"])
+
+    assert errors.issubset(found_errors)