The error occured because aria_copy_to_s3() function tried to copy .frm file
of partition, but partition does not have it's own .frm file. The same is true
for aria_rename_s3().

To fix this issue the new parameter was added to those two functions to specify
if .frm file must be copied or not. The parameter is set to 'false' for
partitions.

Also there was other issue with EXCHANGE PARTITION. Briefly, there is the
following sequence of operations(see  exchange_name_with_ddl_log() for details):
1) rename swap table to temporary table,
2) rename partition to swap table,
3) rename temporary table to partition.

On step (1) .frm file is renamed too. On step (2) the swap table does not
have .frm file, as partition does not have it. On step (3) partition will have
.frm file, because it will be renamed from temporary table. All of this causes
error on different stages of the table access. To fix it, .frm is not touched
at all for s3 during EXCHANGE PARTITION operation. This is implemented in
ha_s3::rename_table() by additional checking of
current_thd->lex->alter_info.partition_flags(see also ALTER_PARTITION_EXCHANGE
in sql_yacc.yy).