BRUSSELS (Reuters) - An interim Brexit deal struck by Theresa May and the European Commission is not legally binding but the British prime minister has committed her government to honoring a gentlemen s agreement, an EU spokesman said on Monday.  Formally speaking, the joint report is not legally binding,  the European Commission s chief spokesman Margaritis Schinas told reporters when asked about suggestions from some of May s ministers that the terms of Friday s accord could change.  But we see the joint report of Michel Barnier and David Davis as a deal between gentlemen and it is the clear understanding that it is fully backed and endorsed by the UK government,  he added, referring to each side s negotiator. Referring to EU chief executive Jean-Claude Juncker, he said:  President Juncker had a meeting with Prime Minister May last Friday morning to ascertain that this is precisely the case. They shook hands.  