Fatal error: The website encountered an unexpected error. Please try again later.

Problem/Motivation

If Ludwig is used to manage the library dependency of some early-bootstrap contributed module, the refreshing the "Reports > Packages" page during the module upgrade can produce the "The website encountered an unexpected error. Please try again later." fatal error message due to missing packages not yet being downloaded.

Steps to reproduce

1. Install Ludwig module ver. 8.x-1.10 or 2.0.1 (or older).
2. Download the Mobile Detect module (-dev version at the moment).
3. Visit the "Reports > Packages" page and download mobile_detect module missing packages.
4. Install the Mobile Detect module.
5. Visit module root folder and imitate the module upgrade by manually deleting the "lib" folder created by Ludwig.
6. Try to refresh the "Reports > Packages" page. The "The website encountered an unexpected error. Please try again later." fatal error is displayed.

Proposed resolution

For the majority of the Ludwig users the "Download and unpack all missing packages" action can be the default action embedded into the Reports > Packages page visit. This would fix the issue with the Reports > Packages page refresh during the upgrade steps of the early-bootstrap modules described above.

Remaining tasks

1. Perform the "Download missing packages" action prior to the Packages page load (/admin/reports/packages).

2. For those who need more control over the missing packages (review and download) - add new "Packages list (skip download)" local action link (tab) at the Packages page.

3. Make the "Download missing packages" button always clickable - even if there are zero packages missing.

User interface changes

1. Rename "Download and unpack all missing packages" button to more simple "Download missing packages".

2. Add new "Packages list (skip download)" local action link (/admin/reports/packages_skip).

Post commit changes

Adjust the online documentation accordingly.