test: prep manual equality assert conversions

The later scripted diff only handles plain `assert x == y` lines.
Some remaining tests still use equality inside comprehensions, parenthesized asserts, and other shapes that the line-based rewrite would misread.
Rewrite those sites by hand first so the later mechanical conversion stays safe.
The commit also simplifies the dead `len(["errors"]) == 0` branch in `blocktools.py`, which can never be true.

test/functional/test_framework/test_framework.py

@@ -673,7 +673,8 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
         `[{"txid": txid, "vout": vout1}, {"txid": txid, "vout": vout2}, ...]`.
         The result can be used to specify inputs for RPCs like `createrawtransaction`,
         `createpsbt`, `lockunspent` etc."""
-        assert all(len(output.keys()) == 1 for output in outputs)
+        for output in outputs:
+            assert_equal(len(output.keys()), 1)
         send_res = node.send(outputs)
         assert send_res["complete"]
         utxos = []