Fix lint errors

app/app.py

@@ -1,5 +1,7 @@
 #!/usr/local/bin/python3
 
+"""Flask web server."""
+
 from flask import Flask, render_template, request
 from app.send_page import send_page
 
@@ -8,10 +10,12 @@ app = Flask(__name__)
 
 @app.route("/", methods=['GET'])
 def index():
+    """Returns index template."""
     return render_template('index.html', status='')
 
 @app.route("/", methods=['POST'])
 def send():
+    """POST function"""
     result = send_page(
         name=request.form.get('name'),
         email=request.form.get('email'),

app/main.py

@@ -1,11 +1,14 @@
 #!/usr/local/bin/python3
 
+"""Main module."""
+
 from app.app import app
 
 
 def main():
+    """Run the app."""
     app.run()
-    
+
 
 if __name__ == "__main__":
     main()

app/send_page.py

@@ -1,10 +1,13 @@
 #!/usr/local/bin/python3
 
+"""Send messages via the Pushover API."""
+
 import os
 import requests
 
 
 def send_page(name: str, email: str, message: str) -> tuple:
+    """POST to the Pushover API."""
     api_url = "https://api.pushover.net/1/messages.json"
     api_token = os.getenv('PUSHOVER_API_TOKEN')
     user_key = os.getenv('PUSHOVER_USER_KEY')