It would be great if more guidance was given in the Trailhead module for this:

Running this under OSX 10.13.4, when doing the first Module ("Get Set Up with GitHub and Travis Continuous Integration"), I was stopped at the "Install the Travis CI Client" step with the error, "You don't have write permissions for the /Library/Ruby/Gems/2.3.0 directory"

You too? See https://stackoverflow.com/questions/34071868/gem-install-git-up-no-longer-working-in-el-capitan/34071869#34071869

You'll have to install Homebrew first, if you haven't done so already: https://brew.sh/ (with thanks to https://stackoverflow.com/questions/20381128/how-to-install-homebrew-on-os-x). 

Am running into an error in the Trailhead module for Packaging2.  I've downloaded the DreamHouse app and created the package without error.  But when I try to create a new version of the package, I get "An unexpected error occurred.  Please contact Salesforce Support and provide the following error code...."  It runs for about 2 minutes before it runs into this error.  I've started over from scratch.  I've remembered to put the pakcage id into the sfdx-project.json file.  I've double-checked that I'm connected to my DevHub.  I've double-checked that the force-app folder has the appropriate contents.  Any ideas where else to look?

Am running into an error in the Trailhead module for Packaging2.  I've downloaded the DreamHouse app and created the package without error.  But when I try to create a new version of the package, I get "An unexpected error occurred.  Please contact Salesforce Support and provide the following error code...."  It runs for about 2 minutes before it runs into this error.  I've started over from scratch.  I've remembered to put the pakcage id into the sfdx-project.json file.  I've double-checked that I'm connected to my DevHub.  I've double-checked that the force-app folder has the appropriate contents.  Any ideas where else to look?

I'm following the Salesforce DX unit "Build the account map display"

When I add the map component and refresh the tab, I get the following error:
 

[cannot use the given object as a weak map key]
n()@https://inspiration-speed-2230-dev-ed.lightning.force.com/auraFW/javascript/1bO4dJePbDnoI-_VdhdsEQ/aura_prod.js:4:277
a()@https://inspiration-speed-2230-dev-ed.lightning.force.com/auraFW/javascript/1bO4dJePbDnoI-_VdhdsEQ/aura_prod.js:4:403
get/<()@https://inspiration-speed-2230-dev-ed.lightning.force.com/auraFW/javascript/1bO4dJePbDnoI-_VdhdsEQ/aura_prod.js:24:77433
{anonymous}()@https://inspiration-speed-2230-dev-ed.lightning.force.com/resource/leaflet/leaflet.js:17:25431
{anonymous}()@https://inspiration-speed-2230-dev-ed.lightning.force.com/resource/leaflet/leaflet.js:17:140
{anonymous}()@https://inspiration-speed-2230-dev-ed.lightning.force.com/resource/leaflet/leaflet.js:17:2
{anonymous}()@https://inspiration-speed-2230-dev-ed.lightning.force.com/resource/leaflet/leaflet.js:11:2
{anonymous}()@https://inspiration-speed-2230-dev-ed.lightning.force.com/resource/leaflet/leaflet.js:7:17

From some cursory Googling, this seems to be related to the new Locker Service not working in Firefox.

Because Locker Services can't be disabled in orgs created in 2018, this unit may need updating.

Notes:

• I don't get this error in Chrome
• I've tried using both the latest version of Leaflet and the version referenced in the text (1.2.0)