Replaced some pexcept() calls with perror().error_cleanup

Converted some strings to f-strings.
Fixed some grammar in error messages and docs.
Increased code coverage.

1 files changed, 1 insertions, 1 deletions

diff --git a/cmd2/parsing.py b/cmd2/parsing.py
index 3dff2689..db5dbd92 100755
--- a/cmd2/parsing.py
+++ b/cmd2/parsing.py
@@ -296,7 +296,7 @@ class StatementParser:
     def is_valid_command(self, word: str, *, is_subcommand: bool = False) -> Tuple[bool, str]:
         """Determine whether a word is a valid name for a command.
 
-        Commands can not include redirection characters, whitespace,
+        Commands cannot include redirection characters, whitespace,
         or termination characters. They also cannot start with a
         shortcut.