Reformatted warning message

Author: kmvanbrunt

cmd2/cmd2.py

@@ -56,9 +56,9 @@
 
 # Set up readline
 if rl_type == RlType.NONE:  # pragma: no cover
-    rl_warning = "Readline features including tab completion have been disabled since no \n" \
-                 "supported version of readline was found. To resolve this, install \n" \
-                 "pyreadline on Windows or gnureadline on Mac.\n\n"
+    rl_warning = ("Readline features including tab completion have been disabled since no\n"
+                  "supported version of readline was found. To resolve this, install pyreadline\n"
+                  "on Windows or gnureadline on Mac.\n\n")
     sys.stderr.write(ansi.style_warning(rl_warning))
 else:
     from .rl_utils import rl_force_redisplay, readline