PythonのPostgreSQL用パッケージ(psycopg2)をインストールしたい

前提・実現したいこと

前提：
Djangogirls tutorialの「PostgreSQLのインストール」で躓きました。
その中の「PythonのPostgreSQL用パッケージのインストール」までは問題なく進められていました。
参考：https://tutorial-extensions.djangogirls.org/ja/optional_postgresql_installation/

同様の問題を取り扱ったstack over flowの記事に書いてある対処法は一通り行いました。
参考：https://stackoverflow.com/questions/12906351/importerror-no-module-named-psycopg2

実現したいこと：

(myvenv) alcohole:~/environment/djangogirls (master) $ python -c "import psycopg2"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'psycopg2'

のMuduleNotFoundErrorを解消したいです。

該当のソースコード

以下は、python, pip, herokuのバージョンの表示、postgreSQLの状態、
そして調べて出てきた対処法を一通り試してみたログとsettings.pyです。

### bash(AWS Cloud9のAmazon Linux)

(myvenv) alcohole:~/environment/djangogirls (master) $ python --version
Python 3.6.8

(myvenv) alcohole:~/environment/djangogirls (master) $ pip --version
pip 19.3.1 from /home/ec2-user/environment/djangogirls/myvenv/lib64/python3.6/dist-packages/pip (python 3.6)

(myvenv) alcohole:~/environment/djangogirls (master) $ heroku -v
heroku-cli/7.0.9 linux-x64 node-v10.16.3

(myvenv) alcohole:~/environment/djangogirls (master) $ psql
psql: FATAL:  role "ec2-user" does not exist

(myvenv) alcohole:~/environment/djangogirls (master) $ sudo -u postgres psql
could not change directory to "/home/ec2-user/environment/djangogirls"
psql (9.2.24)
Type "help" for help.

postgres=# CREATE USER KentoHomma;
ERROR:  role "kentohomma" already exists
postgres=# CREATE DATABASE djangogirls OWNER KentoHomma
postgres-# ;
ERROR:  database "djangogirls" already exists
postgres=# pip install psycopg2
postgres-# ^\

(myvenv) alcohole:~/environment/djangogirls (master) $ pip install psycopg2
Requirement already satisfied: psycopg2 in ./myvenv/lib/python3.6/dist-packages (2.8.4)

(myvenv) alcohole:~/environment/djangogirls (master) $ python -c "import psycopg2"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'psycopg2'

(myvenv) alcohole:~/environment/djangogirls (master) $ pip install psycopg2-binary
Requirement already satisfied: psycopg2-binary in ./myvenv/lib/python3.6/dist-packages (2.8.4)

(myvenv) alcohole:~/environment/djangogirls (master) $ python -c "import psycopg2"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'psycopg2'

(myvenv) alcohole:~/environment/djangogirls (master) $ yum install postgresql-devel-8.4.20-4.el6_7.x86_64
Loaded plugins: priorities, update-motd, upgrade-helper
You need to be root to perform this command.

(myvenv) alcohole:~/environment/djangogirls (master) $ sudo yum install postgresql-devel-8.4.20-4.el6_7.x86_64
Loaded plugins: priorities, update-motd, upgrade-helper
amzn-main                                                                                                                                                                    | 2.1 kB  00:00:00     
amzn-updates                                                                                                                                                                 | 2.5 kB  00:00:00     
1065 packages excluded due to repository priority protections
No package postgresql-devel-8.4.20-4.el6_7.x86_64 available.
Error: Nothing to do

(myvenv) alcohole:~/environment/djangogirls (master) $ yum install python-psycopg2
Loaded plugins: priorities, update-motd, upgrade-helper
You need to be root to perform this command.

(myvenv) alcohole:~/environment/djangogirls (master) $ pip yum install python-psycopg2
ERROR: unknown command "yum"

(myvenv) alcohole:~/environment/djangogirls (master) $ sudo yum install python-psycopg2
Loaded plugins: priorities, update-motd, upgrade-helper
1065 packages excluded due to repository priority protections
Package python26-psycopg2-2.5.1-3.8.amzn1.x86_64 already installed and latest version
Nothing to do

(myvenv) alcohole:~/environment/djangogirls (master) $ python -c "import psycopg2"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'psycopg2'

(myvenv) alcohole:~/environment/djangogirls (master) $ sudo yum install build-dep python-psycopg2
Loaded plugins: priorities, update-motd, upgrade-helper
1065 packages excluded due to repository priority protections
No package build-dep available.
Package python26-psycopg2-2.5.1-3.8.amzn1.x86_64 already installed and latest version
Nothing to do

(myvenv) alcohole:~/environment/djangogirls (master) $ pip install psycopg2 
Requirement already satisfied: psycopg2 in ./myvenv/lib/python3.6/dist-packages (2.8.4)

(myvenv) alcohole:~/environment/djangogirls (master) $ sudo yum install libpq-dev
Loaded plugins: priorities, update-motd, upgrade-helper
1065 packages excluded due to repository priority protections
No package libpq-dev available.
Error: Nothing to do

(myvenv) alcohole:~/environment/djangogirls (master) $ pip install psycopg2
Requirement already satisfied: psycopg2 in ./myvenv/lib/python3.6/dist-packages (2.8.4)

(myvenv) alcohole:~/environment/djangogirls (master) $ sudo python -m pip install psycopg2
Collecting psycopg2
  Downloading https://files.pythonhosted.org/packages/84/d7/6a93c99b5ba4d4d22daa3928b983cec66df4536ca50b22ce5dcac65e4e71/psycopg2-2.8.4.tar.gz (377kB)
    100% |████████████████████████████████| 378kB 2.7MB/s 
Building wheels for collected packages: psycopg2
  Running setup.py bdist_wheel for psycopg2 ... done
  Stored in directory: /root/.cache/pip/wheels/7e/5b/53/30085c62689dcfce50c8f40759945a49eb856af082e9ebf751
Successfully built psycopg2
Installing collected packages: psycopg2
Successfully installed psycopg2-2.8.4
You are using pip version 9.0.3, however version 19.3.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

(myvenv) alcohole:~/environment/djangogirls (master) $ python -c "import psycopg2"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'psycopg2'

(myvenv) alcohole:~/environment/djangogirls (master) $ sudo yum install python3 python-dev python3-dev
Loaded plugins: priorities, update-motd, upgrade-helper
amzn-main                                                                                                                                                                    | 2.1 kB  00:00:00     
amzn-updates                                                                                                                                                                 | 2.5 kB  00:00:00     
1065 packages excluded due to repository priority protections
No package python3 available.
No package python-dev available.
No package python3-dev available.
Error: Nothing to do

(myvenv) alcohole:~/environment/djangogirls (master) $ pip install psycopg2
Requirement already satisfied: psycopg2 in ./myvenv/lib/python3.6/dist-packages (2.8.4)

(myvenv) alcohole:~/environment/djangogirls (master) $ python -c "import psycopg2"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'psycopg2'

(myvenv) alcohole:~/environment/djangogirls (master) $ easy_install psycopg2
Searching for psycopg2
Best match: psycopg2 2.8.4
Adding psycopg2 2.8.4 to easy-install.pth file

Using /home/ec2-user/environment/djangogirls/myvenv/lib/python3.6/dist-packages
Processing dependencies for psycopg2
Finished processing dependencies for psycopg2

(myvenv) alcohole:~/environment/djangogirls (master) $ python -c "import psycopg2"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'psycopg2'

### settings.py(database部分)


DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'djangogirls',
        'USER': 'KentoHomma',
        'PASSWORD': '',
        'HOST': 'localhost',
        'PORT': '',
    }
}