Python: Add psycopg2.pool tests

Author: tausbn

python/ql/test/library-tests/frameworks/psycopg2/ConceptsTest.expected

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+import python
+import experimental.meta.ConceptsTest

python/ql/test/library-tests/frameworks/psycopg2/ConceptsTest.ql

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+# Examples using psycopg2 connection pools.
+
+import psycopg2
+from psycopg2.pool import SimpleConnectionPool, AbstractConnectionPool
+
+
+DSN = "dbname=test user=test password=test host=localhost port=5432"
+
+
+def run_simple_pool_query():
+    pool = SimpleConnectionPool(1, 4, dsn=DSN)
+    try:
+        conn = pool.getconn()
+        try:
+            cur = conn.cursor()
+            try:
+                # Simple, parameterless query
+                cur.execute("SELECT 1") # $ getSql="SELECT 1"
+                _ = cur.fetchall() if hasattr(cur, "fetchall") else None # $ threatModelSource[database]=cur.fetchall()
+            finally:
+                cur.close()
+        finally:
+            pool.putconn(conn)
+    finally:
+        pool.closeall()
+
+
+class LocalPool(AbstractConnectionPool):
+    pass
+
+
+def run_custom_pool_query():
+    pool = LocalPool(1, 3, dsn=DSN)
+    try:
+        conn = pool.getconn()
+        try:
+            cur = conn.cursor()
+            try:
+                cur.execute("SELECT 2") # $ getSql="SELECT 2"
+                _ = cur.fetchone() if hasattr(cur, "fetchone") else None # $ threatModelSource[database]=cur.fetchone()
+            finally:
+                cur.close()
+        finally:
+            pool.putconn(conn)
+    finally:
+        pool.closeall()