Server exception not caught is lock file is not writable

Mon, 27 Jan 2020 22:26:29 GMT solid:get GET -- Error: undefined EACCES: permission denied, mkdir '/Library/WebServer/Documents/profile/card$.ttl.lock'
(node:1964) UnhandledPromiseRejectionWarning: TypeError: releaseLock is not a function
    at Promise (/devel/github.com/solid/node-solid-server/lib/lock.js:25:13)
    at <anonymous>
(node:1964) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 105274)
Mon, 27 Jan 2020 22:26:30 GMT solid:get GET -- Error: undefined EACCES: permission denied, mkdir '/Library/WebServer/Documents/timbl/Public/Archive/linkeddata/chat/2019/08/23/chat.ttl.lock'
(node:1964) UnhandledPromiseRejectionWarning: TypeError: releaseLock is not a function
    at Promise (/devel/github.com/solid/node-solid-server/lib/lock.js:25:13)
    at <anonymous>
(node:1964) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 105275)

Start in lib/lock.js around line 25 and reproduce the EACCES failure when the lock file cannot be created. Trace how the rejected operation reaches the GET handler and verify that the server no longer emits an unhandled promise rejection for this case.