Generating random numbers from custom continuous probability density function

as the title states I am trying to generate random numbers from a custom continuous probability density function, which is:

0.001257 *x^4 * e^(-0.285714 *x)

to do so, I use (on python 3) scipy.stats.rv_continuous and then rvs() to generate them

from decimal import Decimal
from scipy import stats

class my_distribution(stats.rv_continuous):
    def _pdf(self, x):
        return (Decimal(0.001257) *Decimal(x)**(4)*Decimal(np.exp(-0.285714 *x)))

distribution = my_distribution()
distribution.rvs()

note that I used Decimal to get rid of an OverflowError: (34, 'Result too large').

Still, I get an error RuntimeError: Failed to converge after 100 iterations.

What's going on there? What's the proper way to achieve what I need to do?