[Fixed]-Django form not passing is_valid() test

You are writing function based view code inside a class based view, which is incorrect.

You shouldn’t need to instantiate the form, or manually check whether it is valid. Just set form_class for the view, then override form_valid or form_invalid if you need to change the behaviour when the form is valid or invalid. Since you have {{ form.errors }} in your template, it should show any errors when you submit the form.

class PostCreate(generic.CreateView):
    form_class = PostForm
    model = Post

See the docs on form handling with class based views for more information. You might find it easier to write a function based view to begin with, since the flow of the code is easier to follow.