Fix desktop WebSocket certificate verification

desktop-client/test_sync_client.py

@@ -0,0 +1,24 @@
+import ssl
+
+from sync_client import SyncClientThread
+
+
+def test_ssl_context_uses_bundled_ca_certificates():
+    context = SyncClientThread._create_ssl_context()
+
+    assert context.verify_mode == ssl.CERT_REQUIRED
+    assert context.check_hostname is True
+    assert context.cert_store_stats()["x509_ca"] > 0
+
+
+def test_certificate_error_finds_nested_verification_error():
+    certificate_error = ssl.SSLCertVerificationError(1, "certificate has expired")
+
+    try:
+        raise RuntimeError("connection failed") from certificate_error
+    except RuntimeError as error:
+        assert SyncClientThread._certificate_error(error) is certificate_error
+
+
+def test_non_certificate_error_is_ignored():
+    assert SyncClientThread._certificate_error(ConnectionError("offline")) is None