message: Arena does not obsolete but is required by Stadium
diff: <Advisor>ADVISOR_ECONOMY</Advisor>
  <ArtDefineTag>ART_DEF_BUILDING_ARENA</ArtDefineTag>
  <PrereqTech>TECH_ENGINEERING</PrereqTech>
  - <ObsoleteTech>TECH_TELEVISION</ObsoleteTech>
  <iCost>80</iCost>
  <iAdvancedStartCost>100</iAdvancedStartCost>
  <iMinAreaSize>-1</iMinAreaSize>
  <Advisor>ADVISOR_CULTURE</Advisor>
  <ArtDefineTag>ART_DEF_BUILDING_STADIUM</ArtDefineTag>
  <PrereqTech>TECH_TELEVISION</PrereqTech>
  - <iCost>250</iCost>
  + <iCost>200</iCost>
  + <iHappiness>1</iHappiness>
  <iAdvancedStartCost>100</iAdvancedStartCost>
  <iMinAreaSize>-1</iMinAreaSize>
  <iConquestProb>66</iConquestProb>
  - <iHappiness>2</iHappiness>
  <iAsset>4</iAsset>
  <fVisibilityPriority>1.0</fVisibilityPriority>
  <PowerCommerceModifiers>
  <iCommerce>0</iCommerce>
  <iCommerce>25</iCommerce>
  </PowerCommerceModifiers>
  - <CommerceHappinesses>
  - <iCommerce>0</iCommerce>
  - <iCommerce>0</iCommerce>
  - <iCommerce>10</iCommerce>
  - </CommerceHappinesses>
  <BonusHappinessChanges>
  <BonusHappinessChange>
  <BonusType>BONUS_HIT_FOOTBALL_EVENT</BonusType>
  <iHappinessChange>1</iHappinessChange>
  </BonusHappinessChange>
  </BonusHappinessChanges>
  + <BuildingClassNeededs>
  + <BuildingClassNeeded>
  + <BuildingClassType>BUILDINGCLASS_ARENA</BuildingClassType>
  + <bNeededInCity>1</bNeededInCity>
  + </BuildingClassNeeded>
  + </BuildingClassNeededs>
  <ConstructSound>AS2D_BUILD_COLOSSEUM</ConstructSound>
  </BuildingInfo>
  <BuildingInfo>
  