Attempting to check out with a closed OC redirects to homepage

[filipefurtad0]

Description

After inserting items in the cart and while on the /shop page: if the OC closes and the customer tries to proceed to checkout, he will be redirected to the homepage instead of being redirected to the /shop page, where he can select another OC (if available).

Expected Behavior

The customer should be redirected to the /shop page, and if:

1. no other OCs: stay on /shop page where the closed shop message is displayed (as agreed in Fix Grumpy Cat on shop page (cart with items from a closed OC) #5440, Fix Grumpy Cat on shop page (cart with items from a closed OC) #5440 (comment))
2. if there is only one more OC, that one will be selected and displayed
3. if there are two or more OCs, the red Oc selector will show up.

Actual Behaviour

The user is redirected to the homepage and a warning is displayed.

Steps to Reproduce

Taken from: #5501 (comment)

1. Go to shop with (one or) several OC open and add products to the cart, but don't go any further. Stay on the shop page, leave the browser tab opened
2. Close the OC you have just used with another browser window
3. Come back to your tab with the shop
4. Click on the cart on the main menu and "proceed to checkout"

Animated Gif/Screenshot

Redirection to the homepage and display of the warning:

Workaround

Manually select the shop (if open) and an alternative OC, if any.

Severity

bug-s4: it's annoying, but you can use it

Your Environment

• Version used: v2.10
• Browser name and version: Firefox 75
• Operating System and version (desktop or mobile): Desktop Ubuntu 18.04

Possible Fix

Related to #5440.

I think this warning:

only appears when being redirected to the homepage. Which means, after fixing this issue it will not be displayed in any situation, as there will be no redirects to the homepage, due to OC closure. Perhaps this warning could be re-introduced? Would this be a separate papercut, for example?

[filipefurtad0]

This scenario is now triggering a 404 error on checkout:
https://app.bugsnag.com/open-food-france/coopcircuits/errors/609cf8d61cf2950007ce5571?event_id=609d7389007be4c96c350000&i=sk&m=nw

Update: The test above relates to a slightly different scenario - clicking "checkout" on the checkout page, and hence, another issue -> #5372. The "Steps to reproduce" clearly state "Go to shop with (one or) several OC open and add products to the cart, but don't go any further".