Disable truncating in prettytable if terminal size cannot be determined

src/dnsmgr/__init__.py

@@ -55,6 +55,12 @@ def prettytable(field_names, rows, truncate=False):
     for field in t.field_names:
         t.align[field] = 'l'
 
+    if truncate:
+        try:
+            terminal_width = os.get_terminal_size().columns
+        except OSError:
+            truncate = False
+
     if truncate and rows:
         n_cols = len(rows[0])
         max_col_lengths = [0] * n_cols
@@ -66,7 +72,6 @@ def prettytable(field_names, rows, truncate=False):
         max_total_len = sum(max_col_lengths) + 2
         max_pre_len = sum(max_col_lengths[0:-1]) + 2
 
-        terminal_width = os.get_terminal_size().columns
         if max_total_len >= terminal_width:
             max_value_len = terminal_width - max_pre_len - 3
             if max_value_len < 5: