Improve error banner when swimlane sidebar is applied

Problem to solve

When there is an error while reassigning epics in the swimlanes issue sidebar-

• The error messaging is very generic
• The banner covers the sidebar

Intended users

• Parker (Product Manager)
• Delaney (Development Team Lead)
• Presley (Product Designer)
• Sasha (Software Developer)

User experience goal

• Help users understand why they are not able to reassign their epic with clear error messaging.
• Issue sidebar is not covered up and is usable.

Proposal

• Improve the error messaging here. What is the actually problem triggering this error?
• Reduce the width of the banner so that it is "behind" the sidebar

Before	After