Use flask session store instead of DIYing

roc_fnb/util/env_file.py

@@ -0,0 +1,29 @@
+from os import environ
+
+
+def env_file(key, default_file=KeyError, default=KeyError, default_fn=KeyError):
+    """
+    Return a value from an environment variable or file specified by one.
+
+    Checks first for the value specified by key with "_FILE" appended. If that
+    is found, read from the file there. Otherwise return the value of the
+    environment variable, the contents of the specified default file, the default
+    value, or raises KeyError.
+    """
+    if fp := environ.get(f'{key}_FILE'):
+        with open(fp) as file:
+            return file.read()
+    if var := environ.get(key):
+        return var
+    if default_file is not KeyError:
+        try:
+            with open(default_file) as file:
+                return file.read()
+        except FileNotFoundError:
+            ... # fallthrough
+    if default is not KeyError:
+        return default
+    if default_fn is not KeyError:
+        return default_fn()
+    raise KeyError(f'no environment variable found ${key} nor {key}_FILE and default was not specified')   
+