from odoo import api, fields, models
from odoo.exceptions import ValidationError


class InvoiceInh(models.Model):
    _inherit = 'account.move'

    def action_post(self):

        for line in self.invoice_line_ids:
            if not line.analytic_account_id:
                raise ValidationError('Analytic Account field in the products tab is missing.'
                                      ' Please enter it to be able to continue.')

A work-around solution is to add validation code on the 'post' button. Achieved through inheriting that function.

from odoo import models
from odoo.exceptions import ValidationError


class ValidateAccountMove(models.TransientModel):
    _inherit = 'validate.account.move'

    def validate_move(self):
        res = super(ValidateAccountMove, self).validate_move()

        active_ids = self._context.get('active_ids')
        moves = self.env['account.move'].browse(active_ids)
        for line in moves.invoice_line_ids:
            if not line.analytic_account_id:
                raise ValidationError('Analytic Account field in the products tab is missing.'
                                      ' Please enter it to be able to continue.')
        return res

Also this should be added to prevent posting from accounting dashboard using action->post entries