Fix: escape '\n' in row_sep and sep error messages

cloup/formatting/_formatter.py

@@ -114,8 +114,9 @@ def __init__(
         check_positive_int(col_spacing, 'col_spacing')
         if isinstance(row_sep, str) and row_sep.endswith('\n'):
             raise ValueError(
-                "row_sep must not end with '\n'. Since v0.9, the formatter writes "
-                "a '\n' after it. To disable row_sep, you can leave it set to None.")
+                "since v0.9, row_sep must not end with '\\n'. The formatter writes "
+                "a '\\n' after it; no other newline is allowed.\n"
+                "If you want an empty line between rows, set row_sep=''.")
 
         max_width = max_width or 80
         # We subtract 1 to the terminal width to leave space for the new line character.

cloup/formatting/sep.py

@@ -97,8 +97,8 @@ def __init__(self, condition: RowSepCondition,
         """
         if isinstance(sep, str) and sep.endswith('\n'):
             raise ValueError(
-                "sep must not end with '\n'. Since v0.9, the formatter writes "
-                "a '\n' after it.")
+                "sep must not end with '\\n'. The formatter writes  a '\\n' after it; "
+                "no other newline is allowed.")
         self.condition = condition
         self.sep = sep
 

tests/test_formatting.py

@@ -93,7 +93,7 @@ def test_col2_min_width():
 
 
 def test_value_error_if_row_sep_string_ends_with_newline():
-    with pytest.raises(ValueError, match="row_sep must not end with '\n'"):
+    with pytest.raises(ValueError, match=r"row_sep must not end with '\\n'"):
         HelpFormatter(row_sep='\n')
 
 

tests/test_sep.py

@@ -63,7 +63,7 @@ def test_with_percentage(self):
 
 
 def test_value_error_if_sep_string_ends_with_newline():
-    with pytest.raises(ValueError, match="sep must not end with '\n'"):
+    with pytest.raises(ValueError, match=r"sep must not end with '\\n'"):
         RowSepIf(multiline_rows_are_at_least(1), sep='\n')