Sorry, I cut part of the error. It complains about conflicting bundles. The full error is
ERROR: org.eclipse.equinox.p2.director code=0 Software being installed: artificial_root 1.0.0.v1495813449953
ERROR: org.eclipse.equinox.p2.director code=1 Only one of the following can be installed at once:
ERROR: org.eclipse.equinox.p2.director code=0 Papyrus DSML Validation (Incubation) 1.2.0.201705100759 (org.eclipse.papyrus.dsml.validation 1.2.0.201705100759)
ERROR: org.eclipse.equinox.p2.director code=0 Papyrus DSML Validation (Incubation) 1.2.0.201705170313 (org.eclipse.papyrus.dsml.validation 1.2.0.201705170313)
ERROR: org.eclipse.equinox.p2.director code=1 Cannot satisfy dependency:
ERROR: org.eclipse.equinox.p2.director code=0 From: artificial_root 1.0.0.v1495813449953
ERROR: org.eclipse.equinox.p2.director code=0 To: org.eclipse.papyrus.dsml.validation.feature.feature.group 0.0.0
ERROR: org.eclipse.equinox.p2.director code=1 Cannot satisfy dependency:
ERROR: org.eclipse.equinox.p2.director code=0 From: artificial_root 1.0.0.v1495813449953
ERROR: org.eclipse.equinox.p2.director code=0 To: org.eclipse.papyrus.extra.dsml.validation.feature.feature.group 0.0.0
ERROR: org.eclipse.equinox.p2.director code=1 Cannot satisfy dependency:
ERROR: org.eclipse.equinox.p2.director code=0 From: Papyrus DSML Validation Feature (Incubation) 1.2.0.201705100759 (org.eclipse.papyrus.dsml.validation.feature.feature.group 1.2.0.201705100759)
ERROR: org.eclipse.equinox.p2.director code=0 To: org.eclipse.papyrus.dsml.validation [1.2.0.201705100759]
ERROR: org.eclipse.equinox.p2.director code=1 Cannot satisfy dependency:
ERROR: org.eclipse.equinox.p2.director code=0 From: Papyrus DSML Validation Feature (Incubation) 1.2.0.201705170313 (org.eclipse.papyrus.extra.dsml.validation.feature.feature.group 1.2.0.201705170313)
ERROR: org.eclipse.equinox.p2.director code=0 To: org.eclipse.papyrus.dsml.validation [1.2.0.201705170313]
Anyway, I'll try to do a fresh install to see if it works for me.