Suppress E501 in generated prefix util script (#644)

We don't generally enforce linters in generated scripts, but it's easy
enough to add suppressions to these lines, which vary in length based on
the environment.

colcon_core/shell/template/prefix_util.py.em

@@ -15,9 +15,9 @@ FORMAT_STR_SET_ENV_VAR = '@(shell_extension.FORMAT_STR_SET_ENV_VAR)'
 @{assert shell_extension.FORMAT_STR_USE_ENV_VAR is not None}@
 FORMAT_STR_USE_ENV_VAR = '@(shell_extension.FORMAT_STR_USE_ENV_VAR)'
 @{assert shell_extension.FORMAT_STR_INVOKE_SCRIPT is not None}@
-FORMAT_STR_INVOKE_SCRIPT = '@(shell_extension.FORMAT_STR_INVOKE_SCRIPT)'
-FORMAT_STR_REMOVE_LEADING_SEPARATOR = '@(shell_extension.FORMAT_STR_REMOVE_LEADING_SEPARATOR)'
-FORMAT_STR_REMOVE_TRAILING_SEPARATOR = '@(shell_extension.FORMAT_STR_REMOVE_TRAILING_SEPARATOR)'
+FORMAT_STR_INVOKE_SCRIPT = '@(shell_extension.FORMAT_STR_INVOKE_SCRIPT)'  # noqa: E501
+FORMAT_STR_REMOVE_LEADING_SEPARATOR = '@(shell_extension.FORMAT_STR_REMOVE_LEADING_SEPARATOR)'  # noqa: E501
+FORMAT_STR_REMOVE_TRAILING_SEPARATOR = '@(shell_extension.FORMAT_STR_REMOVE_TRAILING_SEPARATOR)'  # noqa: E501
 
 DSV_TYPE_APPEND_NON_DUPLICATE = 'append-non-duplicate'
 DSV_TYPE_PREPEND_NON_DUPLICATE = 'prepend-non-duplicate'