cql-pytest/test_lwt: test LWT update with empty partition range

Add a test case which performs an LWT UPDATE, but the partition key
has 0 possible values, because it's supposed to be equal to two
different values.
Such queries used to cause problems in the past.

Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>

test/cql-pytest/test_lwt.py

@@ -62,3 +62,10 @@ def test_lwt_static_condition(cql, table1):
     # respectively.
     with pytest.raises(InvalidRequest, match=re.compile('missing', re.IGNORECASE)):
         cql.execute(f'UPDATE {table1} SET s=2 WHERE p={p} IF r=1')
+
+# Generate an LWT update where there is no value for the partition key,
+# as the WHERE restricts it using `p = {p} AND p = {p+1}`.
+# Such quries are rejected.
+def test_lwt_empty_partition_range(cql, table1):
+    with pytest.raises(InvalidRequest):
+        cql.execute(f"UPDATE {table1} SET r = 9000 WHERE p = 1 AND p = 1000 AND c = 2 IF r = 3")