HerokuにDjangoアプリをデプロイできません

前提・実現したいこと

Django Girsのチュートリアル
に沿って、git pushコマンドにて
Herokuにデプロイをしたのですが、エラーとなり解決できません。

発生している問題・エラーメッセージ

C:\Users\xxxx\PycharmProjects\djangogirls>git push heroku master
Enumerating objects: 26, done.
Counting objects: 100% (26/26), done.
Delta compression using up to 4 threads.
Compressing objects: 100% (23/23), done.
Writing objects: 100% (26/26), 7.68 KiB | 393.00 KiB/s, done.
Total 26 (delta 0), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Python app detected
remote: ! The latest version of Python 3 is python-3.6.6 (you are using Pyt
hon 3.6.6, which is unsupported).
remote: ! We recommend upgrading by specifying the latest version (python-3
.6.6).
remote: Learn More: https://devcenter.heroku.com/articles/python-runtimes

remote: -----> Installing Python 3.6.6
remote: ! Requested runtime (Python 3.6.6) is not available for this stack
(heroku-16).
remote: ! Aborting. More info: https://devcenter.heroku.com/articles/pytho
n-support
remote: ! Push rejected, failed to compile Python app.
remote:
remote: ! Push failed
remote: Verifying deploy...
remote:
remote: ! Push rejected to ancient-earth-27024.
remote:
To https://git.heroku.com/ancient-earth-27024.git
! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/ancient-earth-27024.g
it'

該当のソースコード

参考までにgit init ～ git pushの手前までに実行したコマンドを記載します

C:\Users\XXXX\PycharmProjects\djangogirls>git init
Initialized empty Git repository in C:/Users/XXXX/PycharmProjects/djangogirls
/.git/

C:\Users\XXXX\PycharmProjects\djangogirls>git config user.name "XXXX Yamah
ara"

C:\Users\XXXX\PycharmProjects\djangogirls>git config user.email xxxx@gmai
l.com

C:\Users\XXXX\PycharmProjects\djangogirls>git status
On branch master

No commits yet

Untracked files:
(use "git add <file>..." to include in what will be committed)

    .gitignore
    .idea/
    Procfile
    blog/
    manage.py
    mysite/
    requirements.txt
    runtime.txt

nothing added to commit but untracked files present (use "git add" to track)

C:\Users\XXXX\PycharmProjects\djangogirls>heroku create
Creating app... done, ⬢ boiling-depths-63630
https://boiling-depths-63630.herokuapp.com/ | https://git.heroku.com/boiling-dep
ths-63630.git

C:\Users\XXXX\PycharmProjects\djangogirls>git push heroku master
error: src refspec master does not match any.
error: failed to push some refs to 'https://git.heroku.com/boiling-depths-63630.
git'

C:\Users\XXXX\PycharmProjects\djangogirls>git add -A .

C:\Users\XXXX\PycharmProjects\djangogirls>git commit -m "My Django Girls app"

[master (root-commit) 06c74d4] My Django Girls app
22 files changed, 601 insertions(+)
create mode 100644 .gitignore
create mode 100644 .idea/djangogirls.iml
create mode 100644 .idea/misc.xml
create mode 100644 .idea/modules.xml
create mode 100644 .idea/vcs.xml
create mode 100644 .idea/workspace.xml
create mode 100644 Procfile
create mode 100644 blog/init.py
create mode 100644 blog/admin.py
create mode 100644 blog/apps.py
create mode 100644 blog/migrations/0001_initial.py
create mode 100644 blog/migrations/init.py
create mode 100644 blog/models.py
create mode 100644 blog/tests.py
create mode 100644 blog/views.py
create mode 100644 manage.py
create mode 100644 mysite/init.py
create mode 100644 mysite/settings.py
create mode 100644 mysite/urls.py
create mode 100644 mysite/wsgi.py
create mode 100644 requirements.txt
create mode 100644 runtime.txt