Merge ~cjwatson/snapstore-client:restore-sync-snap-assertions into snapstore-client:master

[Colin Watson]

Restore _sync_snap_assertions call in _import_snap

William Grant says that he removed this by accident in
6fa0aa1c8bdf3f204aead95c47fe24b41a4fe469.

[Colin Watson (cjwatson)]

I accidentally started this from the wrong branch point, but have now rebased.

[Adam Collard (adam-collard)]

review: Approve

diff --git a/siab_client/logic/dump.py b/siab_client/logic/dump.py
index 559112d..f009cc3 100644
--- a/siab_client/logic/dump.py
+++ b/siab_client/logic/dump.py
@@ -80,6 +80,12 @@ def _import_snap(dir):
             codecs.decode(rev_meta['binary_sha3_384'], 'hex')).decode('ascii')
         for rev_meta in rev_metas.values()]
 
+    # Ensure we have all relevant assertions locally before exposing new
+    # revisions to clients.
+    _sync_snap_assertions(
+        'https://assertions.ubuntu.com/v1/', snap_meta['snap_id'], '16',
+        sha3_384s)
+
     seen_archs = set()
     seen_tracks = set()
     seen_track_risk_archs = set()