MySQL load data infile ERROR 1064
CLIENT SIDE
Before you run this
LOAD DATA local infile '/home/pi/Downloads/load_data_infile.txt' 
INTO TABLE test_tbl FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n';

You need to start mysql client program with --local-file
mysql --local-file -uroot -p

If you wish to have this configured permanantly, add this to ~/.my.cnf
[mysql]
local-infile

This forces the mysql client program to execute.
SERVER SIDE
The mysqld (server side must be started with local_infile) in its my.cnf or my.ini.
Make sure to add this
[mysqld]
local_infile=1

and run
service mysql restart

If you cannot config it and restart it, login to mysql and run
mysql&gt; SELECT @@global.local_infile;

or
mysql&gt; SHOW GLOABL VARIABLES LIKE 'local_infile';

If you get 0, you cannot execute LOAD DATA LOCAL INFILE no matter what you do to the client side.
SUPPLEMENTAL INFO
Running the following command
LOAD DATA local-infile '/home/pi/Downloads/load_data_infile.txt' 
INTO TABLE test_tbl FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n';

Gives the following error

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '-infile '/home/pi/Downloads/load_data_infile.txt' INTO TABLE test_tbl FIELDS TER' at line 1

That's just a straight up syntax error.
Get rid of the dash between local and infile so that it reads
LOAD DATA local infile '/home/pi/Downloads/load_data_infile.txt' 
INTO TABLE test_tbl FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n';