SPI Interface to Call Procedure with Transaction Control Statements

In PG-11, procedures were introduced. In the pg_partman tool, a procedure named run_maintenance_proc was developed to replace run_maintenance function. I was trying to call this procedure in pg_partman with SPI_execute() interface and this is the command being executed:

 I received the following error:

2019-01-02 20:13:04.951 PST [26446] ERROR:  invalid transaction termination
2019-01-02 20:13:04.951 PST [26446] CONTEXT:  PL/pgSQL function partman.run_maintenance_proc(integer,boolean,boolean,boolean) line 45 at COMMIT

Apparently, the transaction control command 'COMMIT' is not allowed in a procedure CALL function. But I can CALL this procedure in psql directly.

According to the documentation of CALL, "If CALL is executed in a transaction block, then the called procedure cannot execute transaction control statements. Transaction control statements are only allowed if CALL is executed in its own transaction." 

Therefore, it looks like that SPI_execute() is calling the procedure within a transaction block. So my question is that is there any SPI interface that can call a procedure with transaction control commands? (I tried to use SPI_connect_ext(SPI_OPT_NONATOMIC) to establish a nonatomic  connection but it doesn't help.)

Thanks,

Jiayi Liu