Basically, you would need to build it in string form.
This could be done through a combination of string interpolation and concatenation.
Here is my quick hack below (I have not shown all the code).
There is a cleaner way to do this, e.g. using templates, but I wanted something that would "just work" for the time being.
first_name = form.cleaned_data['first_name']
last_name = form.cleaned_data['last_name']
start_date = form.cleaned_data['start_date']
number = form.cleaned_data['number']
message = form.cleaned_data['message']
number_of_people = form.cleaned_data['number_of_people']
if is_type == 'admin':
sender = form.cleaned_data['email']
return 'Booking request for "{}" tour starting '.format(tour) + str(start_date) + ' from {} {}.'.format(first_name, last_name) + \
'\n\nNumber of people: {}'.format(number_of_people) + \
'\n\nThe message is as follows: \n\n"' + message + \
'"\n\nSent by: {} {}'.format(first_name, last_name) + '\n' + sender + '\n' + number
elif is_type == 'client':
return 'Dear ' + first_name + ' ' + last_name + ',\n\n' +\
'Your booking request for our "{}" Tour has been received.'.format(tour) + \
'\n\nNumber of people: {}'.format(number_of_people) + \
'\n\nThe message is as follows: \n\n"' + message + \
'"\n\nWe will respond as soon as possible.' +\