mc_font_pack_maker.py

import pygame

pygame.init()
width = 1024
height = 1024

screen = pygame.display.set_mode((width, height))
bg = pygame.Surface((width, height), pygame.SRCALPHA)
font = pygame.font.SysFont("Ubuntu", 64)

for row_y in range(0, height, 64):
    for col_x in range(0, width, 64):
        # Find the correct character
        char_index = (row_y // 64) * 16 + (col_x // 64)
        char = chr(char_index)
        print(col_x, row_y, char_index, char)
        try:
            # Add the character to the font map
            char_img = font.render(char, True, (255, 255, 255))
            char_img.set_colorkey((0, 0, 0))
            char_dimen = char_img.get_rect()
            char_dimen.bottomleft = (col_x, row_y + 64)
            bg.blit(char_img, char_dimen)
        except Exception as e:
            print(e)
            pass

# Save
pygame.image.save(bg, "result.png")

pygame.quit()

For 1.8.9.
You can change "Ubuntu" to whatever font you want.
To use, create a new resource pack (add the base icon + pack.mcmeta), then move the generated result.png to assets/minecraft/textures/font/ascii.png.

Alternatively, just use the Smooth Font mod's config.