override default "go back" action on a web page to go back to main menu

[fábio andrews rocha marques]

Let's say i have a "register a new user" View and on this page, when the user forgets to inform a password or a username, i show a message to him on the same page saying "you forgot the password". The way i do this is by doing this(on my View.py in a function called cadastrarprofessor):

nomeusuario = request.POST['usuario'] #username

nomesenha = request.POST['senha'] #password

nomeemail = request.POST['email'] #email

if not nomeusuario:

return render(request,'cadastro.html',{'cadastrorealizadocomsucesso': False, 'error_message': "informe um usuário", 'nomeemailcadastro':nomeemail, 'nomesenhacadastro':nomesenha})

elif not nomesenha:

return render(request,'cadastro.html',{'cadastrorealizadocomsucesso': False, 'error_message': "informe uma senha", 'nomeemailcadastro':nomeemail, 'nomeusuariocadastro':nomeusuario})

elif not nomeemail:

return render(request,'cadastro.html',{'cadastrorealizadocomsucesso': False, 'error_message': "informe um email", 'nomesenhacadastro':nomesenha, 'nomeusuariocadastro':nomeusuario})

And my template for this page(cadastro.html) is like this:

<meta charset="utf-8"/>

<h1>Cadastro</h1>

<form action="{% url 'cadastrarprofessor' %}" method="post">

{% csrf_token %}

<label for="usuario">Usuário: </label>

{% if nomeusuariocadastro %}

<input id="usuario" type="text" name="usuario" value={{ nomeusuariocadastro }}>

{% else %}

<input id="usuario" type="text" name="usuario" value=""/>

{% endif %}

... (DO THE SAME TO SENHA/PASSWORD AND EMAIL)

<input type="submit" value="Cadastrar"/>

</form>

<form action="{% url 'index' %}" method="post">

<input type="submit" value="Voltar"/>

{% csrf_token %}

</form>

{% if cadastrorealizadocomsucesso is True %}<b>cadastro realizado com sucesso!</b>{% endif %}

{% if error_message %}<p><strong>{{ error_message }}</p></strong>{% endif %}

So, every time the user forgets to mention a username or email or password in this screen, i use render to redirect the user to the same page but this time displaying a error_message. Let's say he did forget to fill the textfield with a username... he goes back to the same page and sees the error message. After that, let's say everything is right and he finally registers a new user, he sees "cadastro realizado com sucesso"(sucessfully registered new user) and stays on the same page. But when he goes back a page, instead of going back to the page before the cadastro.html, he goes back to the same page cadastro.html but displaying the error message for the "you forgot to mention your username". I don't want him to go back to the same page with error message, i want to make him go back to my main menu. 

Is there any way to override the current page "go back" action? Is there a better approach to display error messages on the same page instead of using:

return render(request,'cadastro.html',{'cadastrorealizadocomsucesso': False, 'error_message': "informe um usuário", 'nomeemailcadastro':nomeemail, 'nomesenhacadastro':nomesenha})

?