This bug was fixed in the package ldap-account-manager - 5.7-1
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ldap-account-manager (5.7-1) unstable; urgency=medium
* new upstream release
* LP: #1632193 fixed PHP 7 issue
* LP: #1628937 reload only done when apache is active
-- Roland Gruber Tue, 14 Mar 2017 17:47:23
+
I got the same problem.
It is related to changes from php5 to php7 as far as I can see.
The Ubuntu package is a ldap-account-manager version 5.2 where the statement
for ldap-account-manager 5.3 is "LAM 5.3 with PHP 7 compatibility".
Actually I got several problems after upgrading from Ubuntu 14.0
