Its not as though they would do it off the cuff. And if Germany is in violation of the treaty, it's well within their rights to go to war.
This just happens to be a war the UK can win in a single battle, and cannot possibly lose. It's anything but piracy, your myopic stance on the matter notwithstanding.
Breaking treaties is not enough to go to war. You need a very lot more to trigger a war in those days. We are speaking of the 30's, the time of the illfated League of Nations! Not the 21st century of today with hipocrates ruling in some nations, doing what they want, with no one willing to call them off. (No names to be not insulting, but simply read the news). A minor treaty, like a naval agreement is not enough to trigger a war.
BTW, a minor war at sea perhaps, but with a major escalation risk, you seem to forget. Both UK and France certainly were not strong enough to fight a full blown war, while Germany was more or less ready to do so. (Yes on land, but still a major risk to her neighbours.) Is the UK willing to fight a war against France at the same time? Yes, France would get realy pissed off by an unreliable UK going to war over a minor issue, while France was more or less defenseless still, due to cuts in the defensebudget over the years prior to the late 30's. Fracne would ba allienated from the UK and perhaps even go to war against her, to even the odds, as well as preventing a two front encircling with Germany in the east and UK in the North (Belgium). Compared to Germany France did have a navy of certain power, able enough to defend its shore as well as hurting an enemy at sea, if needed.
As said: The topic is far too simplistic and irrelevant as such. Politcs require a more thourough approach, especially in the 30's.
Conclussion: NO WAR over such an insignificant issue as the breach of a minor naval treaty agreement between the world's biggest navy adn a new born fledgling, which basically was the Kriegsmarine at the time. The Britihs had more arguments to fight wars in other parts of the world (Imperialism still ruling in this period of history), than bringing dissaster uppon their own by foolish single minded issues, that were not important at all.
BTW, the Deutschland class cruiser was bassically a typical heavy cruiser, with the same missionprofile as the old French Armored cruisers of the early 20th century, namely commerceraiding as primary objective. Therefore creating a cruiser with more firepower than aything faster (appart from three British left over battlecruisers) and faster than anything stronger in terms of firepower. As such these ships were correctly rated as heavy cruisers by the German Navy from 1940 on, though orriginally classed as "Panzerschiffe in the capitasl ship group, as they replaced obsolete capital ships of an earlier generation. The missionprofile was typpical for cruiserwarfare, primarily disturbing enemy commerce, as lone wolfs at sea, not in a taskforce, or battlefleet as in capital ships.