Add DPD environment variables to tox.ini

tox.ini

@@ -14,4 +14,5 @@ setenv =
     sqlite: DB_NAME={env:SQLITE_NAME::memory:}
     postgresql: DB_NAME={env:POSTGRESQL_NAME:test}
     mysql: DB_NAME={env:MYSQL_NAME:test}
+passenv=DPD_USER_ID DPD_PASSWORD
 install_command = pip install --pre --find-links https://trydevpi.tryton.org/ {opts} {packages}