add missing Seaborn dependency to LiBis easyconfig

[boegel]

(created using eb --new-pr)
this is caught by 'pip check', but only after fixing a bug in PythonPackage (see easybuilders/easybuild-easyblocks#2114)

[boegel]

Test report by @boegel
SUCCESS
Build succeeded for 1 out of 1 (1 easyconfigs in this PR)
node3411.kirlia.os - Linux centos linux 7.8.2003, x86_64, Intel(R) Xeon(R) Gold 6240 CPU @ 2.60GHz (cascadelake), Python 2.7.5
See https://gist.github.com/0623628033567baab5926547d87650f2 for a full test report.

[boegel]

Test report by @boegel
SUCCESS
Build succeeded for 1 out of 1 (1 easyconfigs in this PR)
node3151.skitty.os - Linux centos linux 7.8.2003, x86_64, Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz (skylake_avx512), Python 3.6.8
See https://gist.github.com/c9a4b6084b90dc7a31bd4b36d105813b for a full test report.

[boegel]

Test report by @boegel
SUCCESS
Build succeeded for 2 out of 2 (1 easyconfigs in this PR)
node2583.golett.os - Linux centos linux 7.8.2003, x86_64, Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz (haswell), Python 2.7.5
See https://gist.github.com/5806d1ef8ce25d633492a17c363a78f8 for a full test report.

[boegel]

Test report by @boegel
SUCCESS
Build succeeded for 1 out of 1 (1 easyconfigs in this PR)
generoso - Linux centos linux 8.2.2004, x86_64, Intel(R) Xeon(R) CPU E5-2667 v3 @ 3.20GHz (haswell), Python 3.6.8
See https://gist.github.com/1ef3f19f052a560302430837ee16100d for a full test report.

[smoors]

Test report by @smoors
FAILED
Build succeeded for 0 out of 2 (1 easyconfigs in this PR)
node254.hydra.os - Linux centos linux 7.7.1908, x86_64, Intel(R) Xeon(R) CPU E5-2683 v4 @ 2.10GHz (broadwell), Python 2.7.5
See https://gist.github.com/f52f501b54fedd595dc74f862b3ebc95 for a full test report.

[smoors]

Test report by @smoors
FAILED
Build succeeded for 0 out of 2 (1 easyconfigs in this PR)
node354.hydra.os - Linux centos linux 7.7.1908, x86_64, Intel(R) Xeon(R) Gold 6148 CPU @ 2.40GHz (skylake_avx512), Python 2.7.5
See https://gist.github.com/86e586d0574621b9108dc777c0668a47 for a full test report.

[migueldiascosta]

Test report by @migueldiascosta
FAILED
Build succeeded for 1 out of 3 (1 easyconfigs in this PR)
sms - Linux centos linux 7.6.1810, x86_64, AMD EPYC 7601 32-Core Processor (zen), Python 2.7.5
See https://gist.github.com/b6a9d1fee00300e762af30636bc9c3d4 for a full test report.

[smoors]

there seems to be a mistake in one of the MOABS sanity checks:

Sanity check failed: sanity check command moabs 2>&1 | grep 'Version : 1.3.9.6' exited with code 1 (output: )

(no output)

[smoors]

apparently some extra added Perl modules are missing in my installation.

[smoors]

Test report by @smoors
SUCCESS
Build succeeded for 2 out of 2 (1 easyconfigs in this PR)
node253.hydra.os - Linux centos linux 7.7.1908, x86_64, Intel(R) Xeon(R) CPU E5-2650 v4 @ 2.20GHz (broadwell), Python 2.7.5
See https://gist.github.com/f9c70490713820028e66a62bfa977641 for a full test report.

[smoors]

lgtm

[smoors]

Going in, thanks @boegel!