Error importing module from within a virtual method field defined in another module

[Lisandro]

I have a virtual method field, and its associated function is defined inside a module.

That function imports another function defined in another module.

And that last function also imports another module.

The virtual method function works ok when I call it from a controller function.

However, if I call that method in the scheduler environment, I have the error "Cannot import module mercadopago"

The virtual method field is defined in db.py like this:

from virtual_methods import set_metodo_pago

db.define_table('sitios',
  Field('nombre'),
  Field.Method('set_metodo_pago', lambda row, metodo_pago: sitios_set_metodo_pago(row, metodo_pago)))

These are my modules:

modules/virtual_methods.py
modules/globals.py
modules/mercadopago.py
modules/scheduler_functions.py

in modules/virtual_methods.py

def set_metodo_pago(row, metodo_pago):
    from globals import get_mercadopago_client
    mp = get_mercadopago_client()
    ...

in modules/globals.py

def get_mercadopago_client():
    import mercadopago
    return MP.client()
    ...

in modules/scheduler_function.py

def instalar_nuevo_sitio(nombre):
   db = current.db
   sitio = db(db.sitios.nombre == nombre).select().first()
   sitio.set_metodo_pago(metodopago='ticket') # this is the line that throws the error

However, the same line works ok if I call it from a controller/function.

What am I missing?

[Lisandro]

I've "fixed" the problem, but I don't understand exactly what was it.

The problem wasn't the import itself, but the moment in wich I was doing it.

Let's go back to the function that had the error, here with more detail

def instalar_nuevo_sitio(nombre):

    sitio = db(db.sitios.nombre == nombre).select().first()

    # here it does a lot of stuff
    sitio.set_metodo_pago(metodopago='ticket')  # this line throws the error

Notice the comment where I say that in that place, the function does "a lot of stuff". What is that stuff? Well, what the function does is to install a new app in web2py, that is, clonning the repository and putting all the files needed by the new app. 

How did I solve it? I just moved the sentence to the top, before doing that "lot of stuff".

I don't know why exactly that worked, because the line that throwed the error doesn't have anything to do with the new application installed by the function.

Anyway, It's solved now, but I cannot say why :/