first deploy on heroku fails during the CLI compilation

[Dlacreme]

Hello,

I've followed the documentation to deploy Amber on Heroku.
However, I got this error (full log)

Showing last frame. Use --error-trace for full trace.
In lib/mysql/src/mysql/connection.cr:31:12
 31 | rescue Errno
             ^----
Error: Errno is not a subclass of Exception
Semantic (main):                  
 !     Push failed

It happens during the task:
'-----> Amber CLI not compiled... -----> Installing amber CLI... Resolving dependencies'

I am using:

• Crystal: v0.34.0 (shown in the log even though my shard.yml target v0.33? weird)
• Amber: v.0.33.0

What I've tried to so do far:

• [FAILED] install a MySQL add-on on heroku (thinking that it would add some missing dependencies)
• [FAILED] add 'crystal-lang/crystal-mysql' to shards.yml

Thank you for your time,

[Dlacreme]

I've upgraded my project to Crystal v0.34 and the problem disappeared.