Improve DbC doc for get_access_token()

and fix post-condition on `get_netrc_credentials()`

eof/_auth.py

@@ -87,7 +87,12 @@ def _file_is_0600(filename: Filename):
 
 
 def get_netrc_credentials(host: str, netrc_file: Optional[Filename] = None) -> tuple[str, str]:
-    """Get username and password from netrc file for a given host."""
+    """
+    Get username and password from netrc file for a given host.
+
+    :return: username and password found for host in netrc_file
+    :postcondition: username and password are non empty strings.
+    """
     netrc_file = netrc_file or "~/.netrc"
     netrc_file = Path(netrc_file).expanduser()
     _logger.debug(f"Using {netrc_file=!r}")
@@ -98,6 +103,8 @@ def get_netrc_credentials(host: str, netrc_file: Optional[Filename] = None) -> t
     username, _, password = auth
     if username is None or password is None:
         raise ValueError(f"No username/password found for {host} in ~/.netrc")
+    if not username or not password:
+        raise ValueError(f"Empty username/password found for {host} in ~/.netrc")
     return username, password
 
 

eof/dataspace_client.py

@@ -291,10 +291,12 @@ def query_orbit_file_service(query: str) -> list[dict]:
     return query_results
 
 
-def get_access_token(username, password, token_2fa) -> str:
+def get_access_token(username: str, password: str, token_2fa: Optional[str]) -> str:
     """Get an access token for the Copernicus Data Space Ecosystem (CDSE) API.
 
     Code from https://documentation.dataspace.copernicus.eu/APIs/Token.html
+
+    :precondition: username and password are non empty strings.
     """
     assert username and password, "Username and password values are expected!"