String concatenation in loop causes production risks

This code insight counts one violation each time an operator + or += is used with a string parameter inside a loop.

Note : the rule is restricted to expression with litteral string. Variable string need semantic to be detected.

bad

employee_table = '<table>'
    for last_name, first_name in employee_list:
        employee_table += '<tr><td>%s, %s</td></tr>' % (last_name, first_name)
        employee_table += '</table>'

good

items = ['<table>']
    for last_name, first_name in employee_list:
        items.append('<tr><td>%s, %s</td></tr>' % (last_name, first_name))
        items.append('</table>')
    employee_table = ''.join(items)