def lookup(self, section, name):
value = os.environ.get('<STR_LIT>'.format(name.upper()))<EOL>if value:<EOL><INDENT>return value<EOL><DEDENT>try:<EOL><INDENT>value = self.file_config.get(section, name)<EOL><DEDENT>except ConfigParserError:<EOL><INDENT>pass<EOL><DEDENT>else:<EOL><INDENT>if value:<EOL><INDENT>return value<EOL><DEDENT><DEDENT>raise MissingConfigurationError(section, name)<EOL>
Lookup config value.