use the class method to (un)escape binary values

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -455,14 +455,14 @@ def table_alias_length
 
       # Escapes binary strings for bytea input to the database.
       def escape_bytea(value)
-        @connection.escape_bytea(value) if value
+        PGconn.escape_bytea(value) if value
       end
 
       # Unescapes bytea output from a database to the binary string it represents.
       # NOTE: This is NOT an inverse of escape_bytea! This is only to be used
       #       on escaped binary output from database drive.
       def unescape_bytea(value)
-        @connection.unescape_bytea(value) if value
+        PGconn.unescape_bytea(value) if value
       end
 
       # Quotes PostgreSQL-specific data types for SQL input.