If the release already has a front cover art, adding a second one fails:
(same issue probably exists with back cover arts)

Caught exception in MusicBrainz::Server::Controller::Release->add_cover_art "The edit could not be created.
POST: $VAR1 =

Unknown macro: { 'add-cover-art.id' => '290968060', 'add-cover-art.filename' => 'mbid-b705dcee-a011-4bf0-abf2-4c4d9d586e9e-290968060.jpg', 'add-cover-art.type_id' => '2', 'add-cover-art.position' => '5', 'add-cover-art.comment' => '', 'add-cover-art.edit_note' => '2nd front' }

;

Exception:$VAR1 = 'Failed query:
\'INSERT INTO cover_art_archive.cover_art (release, edit, ordering, id, is_front, is_back, comment)
VALUES (?, ?, ?, ?, ?, ?, ?)\'
(720552 16086254 5 290968060 1 0 )
DBD::Pg::st execute failed: ERROR: duplicate key value violates unique constraint "cover_art_unique_front_constraint"
DETAIL: Key (release, is_front)=(720552, t) already exists. at lib/Sql.pm line 103.

at lib/Sql.pm line 109
Sql::_ANON_(\'DBD::Pg::st execute failed: ERROR: duplicate key value viola...\') called at /home/musicbrainz/perl5/lib/perl5/Try/Tiny.pm line 100
Try::Tiny::try(\'CODE(0x1050e2f0)\', \'Try::Tiny::Catch=REF(0x104900a0)\') called at lib/Sql.pm line 110
Sql::do(\'Sql=HASH(0xd903e00)\', \'INSERT INTO cover_art_archive.cover_art (release, edit, order...\', 720552, 16086254, 5, 290968060, 1, 0, \'\', ...) called at lib/MusicBrainz/Server/Data/CoverArtArchive.pm line 213
MusicBrainz::Server::Data::CoverArtArchive::insert_cover_art(\'MusicBrainz::Server::Data::CoverArtArchive=HASH(0x9f51db0)\', 720552, 16086254, 290968060, 5, \'ARRAY(0x1050da08)\', \'\') called at lib/MusicBrainz/Server/Edit/Release/AddCoverArt.pm line 93
MusicBrainz::Server::Edit::Release::AddCoverArt::insert(\'MusicBrainz::Server::Edit::Release::AddCoverArt=HASH(0x10524040)\') called at lib/MusicBrainz/Server/Data/Edit.pm line 405
MusicBrainz::Server::Data::Edit::_ANON_() called at lib/Sql.pm line 264
Sql::_ANON_() called at /home/musicbrainz/perl5/lib/perl5/Try/Tiny.pm line 76
eval

Unknown macro: {...}

called at /home/musicbrainz/perl5/lib/perl5/Try/Tiny.pm line 67
Try::Tiny::try(\'CODE(0x104ee028)\', \'Try::Tiny::Catch=REF(0x1047a578)\') called at lib/Sql.pm line 277
Sql::_auto_transaction(\'CODE(0x10524028)\', \'Sql=HASH(0xd903e00)\') called at lib/Sql.pm line 282
Sql::_run_in_transaction_one(\'CODE(0x10524028)\', \'Sql=HASH(0xd903e00)\') called at lib/Sql.pm line 296
Sql::run_in_transaction(\'CODE(0x10524028)\', \'Sql=HASH(0xd903e00)\') called at lib/MusicBrainz/Server/Data/Edit.pm line 426
MusicBrainz::Server::Data::Edit::create(\'MusicBrainz::Server::Data::Edit=HASH(0xaf3ceb8)\', \'editor_id\', 29366, \'privileges\', 0, \'cover_art_types\', \'ARRAY(0x1050da08)\', \'cover_art_id\', 290968060, ...) called at lib/MusicBrainz/Server/Controller.pm line 83
MusicBrainz::Server::Controller::_ANON_() called at /home/musicbrainz/perl5/lib/perl5/Try/Tiny.pm line 76
eval

called at /home/musicbrainz/perl5/lib/perl5/Try/Tiny.pm line 67
Try::Tiny::try(\'CODE(0xdd7cb90)\', \'Try::Tiny::Catch=REF(0x104fc8b0)\') called at lib/MusicBrainz/Server/Controller.pm line 99
MusicBrainz::Server::Controller::_insert_edit(\'MusicBrainz::Server::Controller::Release=HASH(0xc462458)\', \'MusicBrainz::Server=HASH(0xca4db60)\', \'MusicBrainz::Server::Form::Release::AddCoverArt=HASH(0xe1fce70)\', \'edit_type\', 314, \'release\', \'MusicBrainz::Server::Entity::Release=HASH(0xe3b42b0)\', \'cover_art_url\', \'mbid-b705dcee-a011-4bf0-abf2-4c4d9d586e9e-290968060.jpg\', ...) called at lib/MusicBrainz/Server/Controller/Release.pm line 424
MusicBrainz::Server::Controller::Release::add_cover_art(\'MusicBrainz::Server::Controller::Release=HASH(0xc462458)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Action.pm line 65
Catalyst::Action::execute(\'Catalyst::Action=HASH(0xc803598)\', \'MusicBrainz::Server::Controller::Release=HASH(0xc462458)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 1667
eval

Unknown macro: {...}

called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 1667
Catalyst::execute(\'MusicBrainz::Server=HASH(0xca4db60)\', \'MusicBrainz::Server::Controller::Release\', \'Catalyst::Action=HASH(0xc803598)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Plugin/StackTrace.pm line 94
Catalyst::Plugin::StackTrace::execute(\'MusicBrainz::Server=HASH(0xca4db60)\', \'MusicBrainz::Server::Controller::Release\', \'Catalyst::Action=HASH(0xc803598)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Action.pm line 60
Catalyst::Action::dispatch(\'Catalyst::Action=HASH(0xc803598)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/ActionChain.pm line 38
Catalyst::ActionChain::dispatch(\'Catalyst::ActionChain=HASH(0xdd7cd58)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Controller.pm line 125
Catalyst::Controller::_ACTION(\'MusicBrainz::Server::Controller::Release=HASH(0xc462458)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Action.pm line 65
Catalyst::Action::execute(\'Catalyst::Action=HASH(0xc7fc650)\', \'MusicBrainz::Server::Controller::Release=HASH(0xc462458)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 1667
eval

called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 1667
Catalyst::execute(\'MusicBrainz::Server=HASH(0xca4db60)\', \'MusicBrainz::Server::Controller::Release\', \'Catalyst::Action=HASH(0xc7fc650)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Plugin/StackTrace.pm line 94
Catalyst::Plugin::StackTrace::execute(\'MusicBrainz::Server=HASH(0xca4db60)\', \'MusicBrainz::Server::Controller::Release\', \'Catalyst::Action=HASH(0xc7fc650)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Action.pm line 60
Catalyst::Action::dispatch(\'Catalyst::Action=HASH(0xc7fc650)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Dispatcher.pm line 257
Catalyst::Dispatcher::_do_forward(\'Catalyst::Dispatcher=HASH(0x38be4a0)\', \'forward\', \'MusicBrainz::Server=HASH(0xca4db60)\', \'_ACTION\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Dispatcher.pm line 237
Catalyst::Dispatcher::forward(\'Catalyst::Dispatcher=HASH(0x38be4a0)\', \'MusicBrainz::Server=HASH(0xca4db60)\', \'_ACTION\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 342
Catalyst::forward(\'MusicBrainz::Server=HASH(0xca4db60)\', \'_ACTION\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Controller.pm line 99
Catalyst::Controller::_DISPATCH(\'MusicBrainz::Server::Controller::Release=HASH(0xc462458)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Action.pm line 65
Catalyst::Action::execute(\'Catalyst::Action=HASH(0xc7fbfa8)\', \'MusicBrainz::Server::Controller::Release=HASH(0xc462458)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 1667
eval

Unknown macro: {...}

called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 1667
Catalyst::execute(\'MusicBrainz::Server=HASH(0xca4db60)\', \'MusicBrainz::Server::Controller::Release\', \'Catalyst::Action=HASH(0xc7fbfa8)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Plugin/StackTrace.pm line 94
Catalyst::Plugin::StackTrace::execute(\'MusicBrainz::Server=HASH(0xca4db60)\', \'MusicBrainz::Server::Controller::Release\', \'Catalyst::Action=HASH(0xc7fbfa8)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Action.pm line 60
Catalyst::Action::dispatch(\'Catalyst::Action=HASH(0xc7fbfa8)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Dispatcher.pm line 257
Catalyst::Dispatcher::_do_forward(\'Catalyst::Dispatcher=HASH(0x38be4a0)\', \'forward\', \'MusicBrainz::Server=HASH(0xca4db60)\', \'/release/_DISPATCH\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Dispatcher.pm line 237
Catalyst::Dispatcher::forward(\'Catalyst::Dispatcher=HASH(0x38be4a0)\', \'MusicBrainz::Server=HASH(0xca4db60)\', \'/release/_DISPATCH\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 342
Catalyst::forward(\'MusicBrainz::Server=HASH(0xca4db60)\', \'/release/_DISPATCH\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Dispatcher.pm line 105
Catalyst::Dispatcher::dispatch(\'Catalyst::Dispatcher=HASH(0x38be4a0)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 1613
Catalyst::dispatch(\'MusicBrainz::Server=HASH(0xca4db60)\') called at lib/MusicBrainz/Server.pm line 264
Class::MOP::Class:::around(\'CODE(0x3492178)\', \'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/x86_64-linux-gnu-thread-multi/Class/MOP/Method/Wrapped.pm line 162
Class::MOP::Method::Wrapped::_ANON_(\'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/x86_64-linux-gnu-thread-multi/Class/MOP/Method/Wrapped.pm line 91
MusicBrainz::Server::dispatch(\'MusicBrainz::Server=HASH(0xca4db60)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 1963
Catalyst::_ANON_() called at /home/musicbrainz/perl5/lib/perl5/Try/Tiny.pm line 76
eval

called at /home/musicbrainz/perl5/lib/perl5/Try/Tiny.pm line 67
Try::Tiny::try(\'CODE(0xca4db00)\', \'Try::Tiny::Catch=REF(0xe10e0a8)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst.pm line 1969
Catalyst::handle_request(\'MusicBrainz::Server\', \'env\', \'HASH(0xc9f0408)\') called at /home/musicbrainz/perl5/lib/perl5/Catalyst/Engine.pm line 856
Catalyst::Engine::_ANON_(\'CODE(0xd8f7ba0)\') called at /home/musicbrainz/perl5/lib/perl5/Plack/Handler/FCGI.pm line 134
Plack::Handler::FCGI::run(\'Plack::Handler::FCGI=HASH(0x18e9928)\', \'CODE(0xc9cf020)\') called at /home/musicbrainz/perl5/lib/perl5/Plack/Loader.pm line 88
Plack::Loader::run(\'Plack::Loader=HASH(0x18bee28)\', \'Plack::Handler::FCGI=HASH(0x18e9928)\') called at /home/musicbrainz/perl5/lib/perl5/Plack/Runner.pm line 263
Plack::Runner::run(\'Plack::Runner=HASH(0x16b4a78)\') called at /home/musicbrainz/perl5/bin/plackup line 10
at lib/Sql.pm line 277
';
at lib/MusicBrainz/Server/Controller.pm line 99"

Stack trace:

line 95 MusicBrainz::Server::Controller
line 99 MusicBrainz::Server::Controller
line 424 MusicBrainz::Server::Controller::Release
line 264 MusicBrainz::Server

Request data:

$VAR1 = {
'query_parameters' => {},
'body_parameters' =>

Unknown macro: { 'add-cover-art.id' => '290968060', 'add-cover-art.type_id' => '2', 'add-cover-art.filename' => 'mbid-b705dcee-a011-4bf0-abf2-4c4d9d586e9e-290968060.jpg', 'add-cover-art.edit_note' => '2nd front', 'add-cover-art.comment' => '', 'add-cover-art.position' => '5' }

};

URL: http://test.musicbrainz.org/release/b705dcee-a011-4bf0-abf2-4c4d9d586e9e/add-cover-art