By Benoit Van Overstraeten and Sudip Kar-Gupta PARIS (Reuters) -Regional train traffic in France was cut by about half on Tuesday as several unions called a nationwide strike, seeking to capitalise on anger with decades-high inflation to expand a weeks-long industrial action at oil refineries to other sectors. There were also some disruption to schools, as the strike primarily affected the public sector. Trade union leaders were hoping workers would be energised by the government’s decision to force some of them to go back to work at petrol depots to try and get fuel flowing again, a decision …