Use secret.txt file auto-generated in project root as default SECRET_KEY

Also add it to .gitignore

.gitignore

@@ -4,6 +4,8 @@ Session.vim
 /.venv
 /.coverage
 /htmlcov
+/secret.txt
+/static
 
 __pycache__
 .*.swp

etesync_server/settings.py

@@ -11,6 +11,7 @@ https://docs.djangoproject.com/en/1.10/ref/settings/
 """
 
 import os
+from django.core.management import utils
 
 # Build paths inside the project like this: os.path.join(BASE_DIR, ...)
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
@@ -20,7 +21,15 @@ BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 # See https://docs.djangoproject.com/en/1.10/howto/deployment/checklist/
 
 # SECURITY WARNING: keep the secret key used in production secret!
-SECRET_KEY = ''
+SECRET_KEY_FILE = os.path.join(BASE_DIR, "secret.txt")
+
+try:
+    with open(SECRET_KEY_FILE, "r") as f:
+        SECRET_KEY = f.read().strip()
+except EnvironmentError:
+    with open(SECRET_KEY_FILE, "w") as f:
+        SECRET_KEY = utils.get_random_secret_key()
+        f.write(SECRET_KEY)
 
 # SECURITY WARNING: don't run with debug turned on in production!
 DEBUG = False