Changes encoding from 'ascii' to 'utf-8'

Reasons:
- Heat code, while encoding the template encodes it with 'ascii'
  encoding, which should be 'utf-8' instead.

Changes:
- Encoding format changed from 'ascii' to 'utf-8'.

Closes-Bug: #1272053
Change-Id: I66a7c20716899144653b7dbc6811c268caaf7c2c