Add MANIFEST.in and Make Download Schema Accessible Through Module

[Aequitosh]

While packaging debsbom for Debian, I found that some tests would fail when ran by pybuild, because it is assumed that schema-download.json in a fixed path relative to the tests/ directory (L270):

debsbom/tests/test_download.py

Lines 268 to 273 in d8dd472

	@pytest.fixture(scope="session")
	def dlschema():
	schemapath = Path(__file__).parent / "../src/debsbom/schema/schema-download.json"
	with open(schemapath) as f:
	schema = json.load(f)
	return schema

So, instead of loading schema-download.json in the fixture, make debsbom.schema a proper Python module and load it during module import. This makes the JSON accessible without requiring a specific directory structure.

I got the idea for this from the following band-aid fix I used for our internal packaging:

diff --git a/tests/test_download.py b/tests/test_download.py
index 5e7ccf2..672bbde 100644
--- a/tests/test_download.py
+++ b/tests/test_download.py
@@ -259,6 +259,10 @@ def test_srcpkg_with_checksum(sdl):
 @pytest.fixture(scope="session")
 def dlschema():
     schemapath = Path(__file__).parent / "../src/debsbom/schema/schema-download.json"
+
+    if not schemapath.exists():
+        schemapath = Path(__file__).parent / "../debsbom/schema/schema-download.json"
+
     with open(schemapath) as f:
         schema = json.load(f)
     return schema

Since that felt a bit too dirty to upstream, I cooked up this PR instead.

Edit: Added acc8e9a, which I was originally planning to add through a separate PR; it adds a MANIFEST.in file that ensures that everything under src/ is included in the built package. This is necessary to make schema-download.json accessible.

[Aequitosh]

Ah, nevermind, this fails in CI:

ERROR tests/test_download.py - FileNotFoundError: [Errno 2] No such file or directory: '/opt/hostedtoolcache/Python/3.11.14/x64/lib/python3.11/site-packages/debsbom/schema/schema-download.json'

I wonder why it's included in the .whl for me locally, but not here... will see if I can find a fix.

[Aequitosh]

Alright, seems good now. Sorry for the noise.