Please see the patch attached in this review: https://reviews.freebsd.org/D13344
A commit references this bug: Author: feld Date: Sun Dec 17 15:13:36 UTC 2017 New revision: 456535 URL: https://svnweb.freebsd.org/changeset/ports/456535 Log: net-mgmt/observium: Update to 0.17.9.8859 - Fixes fetching as upstream always replaces/re-rolls distfile - Now reportedly works with PHP 7.1 PR: 224223 MFH: 2017Q4 Changes: head/net-mgmt/observium/Makefile head/net-mgmt/observium/distinfo head/net-mgmt/observium/files/patch-includes_defaults.inc.php head/net-mgmt/observium/files/patch-poller-wrapper.py head/net-mgmt/observium/files/patch-poller.php head/net-mgmt/observium/pkg-plist
Committed and closing. As upstream re-rolls the distfile every release and essentially breaks the port unless you fetch from FreeBSD distcache, this is a necessary update.
A commit references this bug: Author: feld Date: Sun Dec 17 15:14:50 UTC 2017 New revision: 456536 URL: https://svnweb.freebsd.org/changeset/ports/456536 Log: MFH: r456535 net-mgmt/observium: Update to 0.17.9.8859 - Fixes fetching as upstream always replaces/re-rolls distfile - Now reportedly works with PHP 7.1 PR: 224223 Changes: _U branches/2017Q4/ branches/2017Q4/net-mgmt/observium/Makefile branches/2017Q4/net-mgmt/observium/distinfo branches/2017Q4/net-mgmt/observium/files/patch-includes_defaults.inc.php branches/2017Q4/net-mgmt/observium/files/patch-poller-wrapper.py branches/2017Q4/net-mgmt/observium/files/patch-poller.php branches/2017Q4/net-mgmt/observium/pkg-plist