We have a customer whose base unit for selling stuff is in thousands.  However stock can be as low as 0.001 thousands, but that last decimal place isn't displayed in the stock warning.

As you'll see from the example of "actual behaviour" below this is confusing.

Impacted versions:
- 8.0

Steps to reproduce:
- Install product and sale
- Create a unit of measure with:
  - Name: Thousand(s)
  - Product Category: Unit
  - Type: Bigger than the reference Unit of Measure
  - Bigger Ratio: 1000
  - Rounding Precision: 0.00100
- Create a product 'Widget' with
  - type = Stockable Product
  - UoM = Thousand(s)
- Create a Quotation
- Add to the Sales Order a line
- Choose Product: Widget
- Change Quantity to: 0.001 Thousand(s)

Current behavior:

Configuration Error!

```
Not enough stock ! : You plan to sell 0.00 Thousand(s) but you only have 0.00 Thousand(s) available !
The real stock is 0.00 Thousand(s). (without reservations)
```

Expected behavior:

Configuration Error!

```
Not enough stock ! : You plan to sell 0.001 Thousand(s) but you only have 0.000 Thousand(s) available !
The real stock is 0.000 Thousand(s). (without reservations)
```

addons/sale_stock/models/sale_order.py
from datetime import datetime, timedelta
from odoo import api, fields, models, _
from odoo.tools import DEFAULT_SERVER_DATETIME_FORMAT, float_compare
from odoo.exceptions import UserError
class SaleOrder(models.Model):