App names can no longer end with hyphen (dash)
Change effective on 28 November 2018
Heroku previously allowed app names that ended with a hyphen (dash). Because app names are used in the default app hostname (<appname>.herokuapp.com) and because hostname labels (the parts between the periods in a hostname) are not generally permitted to have trailing hyphens, this caused default app hostnames to be invalid for apps named with a trailing hyphen.
Heroku no longer permits trailing hyphens in newly created app names or when apps are renamed.
Apps previously created with names with trailing hyphens have not been changed, but may have impaired functionality. Heroku recommends renaming apps to not have trailing hyphens.