Do not error if the SUDO_USER can not be looked upbugfix/real-pbuilder-user

This is not an error, it may happen if e.g. sudo is used to enter a chroot. This is what pbulider is doing and RealUser() breaks building snapd with pbuilder (a very common use-case). 

1 files changed, 4 insertions, 0 deletions

diff --git a/osutil/user.go b/osutil/user.go
index afcc59f238..545e18d210 100644
--- a/osutil/user.go
+++ b/osutil/user.go
@@ -83,6 +83,10 @@ func RealUser() (*user.User, error) {
	}
 
	real, err := user.Lookup(realName)
+	// can happen when sudo is used to enter a chroot (e.g. pbuilder)
+	if _, ok := err.(user.UnknownUserError); ok {
+	return cur, nil
+	}
	if err != nil {
	return nil, err
	}