because they're referencing the removed logdiff API.
logdiff
This API was removed in 4d1816b1529e4877f9527f039facbe9953c187bd.
Fixes #409
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OIBSCXGIVF2MKTICVICURPOH63D5I5KHNCUD76KA33A6JYGDPJUAC
2GUAKGTBTNFFER343SQWSLFYIXXHJLDSGH5JHF7QMC3AVZB7Q3TQC
J5UVLXOK6EDIL5I7VKWH4V2QDS4DPD7FHRK6XBWSXFRQS4JKXFZQC
<a class="btn btn-mini" href="[% c.uri_for(c.controller('API').action_for('logdiff') prevSuccessfulBuild.id firstBrokenBuild.id ) %]">log diff</a>
<a class="btn btn-mini" href="[% c.uri_for(c.controller('API').action_for('logdiff') prevSuccessfulBuild.id build.id) %]">log diff</a>