octal values: simpler test for match objects

From the Python 3 documentation:
	Match objects always have a boolean value of True.
	Since match() and search() return None when there is no match,
	you can test whether there was a match with a simple if statement:
		match = re.search(pattern, string)
		if match:
		    process(match)

yamllint/rules/octal_values.py

@@ -96,7 +96,7 @@ def check(conf, token, prev, next, nextnext, context):
             if not token.style:
                 val = token.value
                 if (val.isdigit() and len(val) > 1 and val[0] == '0' and
-                        IS_OCTAL_NUMBER_PATTERN.match(val[1:]) is not None):
+                        IS_OCTAL_NUMBER_PATTERN.match(val[1:])):
                     yield LintProblem(
                         token.start_mark.line + 1, token.end_mark.column + 1,
                         'forbidden implicit octal value "%s"' %
@@ -107,7 +107,7 @@ def check(conf, token, prev, next, nextnext, context):
             if not token.style:
                 val = token.value
                 if (len(val) > 2 and val[:2] == '0o' and
-                        IS_OCTAL_NUMBER_PATTERN.match(val[2:]) is not None):
+                        IS_OCTAL_NUMBER_PATTERN.match(val[2:])):
                     yield LintProblem(
                         token.start_mark.line + 1, token.end_mark.column + 1,
                         'forbidden explicit octal value "%s"' %