rasa: Heroku Deploy Error: No matching distribution found for tensorflow~=1.15.0

Rasa version: 1.16.0

Rasa SDK version (if used & relevant):

Rasa X version (if used & relevant):

Python version: 3.7.5

Operating system (windows, osx, …): OSx & Heroku

Issue: When I tried to deploy my RASA-chatbot on Heroku, I am getting an error during push due to TensorFlow version inconsistency.

Error (including full traceback):

remote:          Could not find a version that satisfies the requirement tensorflow~=1.15.0 (from rasa->-r /tmp/build_eb547afa20c8e3e443b80d37cc63b6cd/requirements.txt (line 1)) (from versions: 1.13.0rc1, 1.13.0rc2, 1.13.1, 1.13.2, 1.14.0rc0, 1.14.0rc1, 1.14.0, 2.0.0a0, 2.0.0b0, 2.0.0b1)
remote:        No matching distribution found for tensorflow~=1.15.0 (from rasa->-r /tmp/build_eb547afa20c8e3e443b80d37cc63b6cd/requirements.txt (line 1))
remote:  !     Push rejected, failed to compile Python app.
remote: 
remote:  !     Push failed
remote: Verifying deploy...
remote: 
remote: !	Push rejected to tabip-chatbot.
remote: 
To https://git.heroku.com/tabip-chatbot.git
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/tabip-chatbot.git'

Command or request that led to error:

Inconsistency with TensorFlow version and pip version(on Heroku?).

Content of configuration file (config.yml) (if relevant):

Content of domain file (domain.yml) (if relevant):