WARNING: nonstandard use of escape in a string literal

This is just a warning. You can either ignore or change the code that sends SQL queries to use standart-string literal.

to remove it from log file open postgresql.conf and edit line :

escape_string_warning = on
change it to 
escape_string_warning = off

or you can just change log behavior

log_min_messages = warning                # values in order of decreasing detail:change it to 
log_min_messages = error