ggplotd hangs often

[wilzbach]

+ ./travis.sh
Generating test runner configuration 'ggplotd-test-default' for 'default' (library).
Performing "unittest" build using dmd for x86_64.
derelict-util 2.1.0: building configuration "library"...
derelict-ft 1.0.2: building configuration "library"...
x11 1.0.19: building configuration "library"...
../../.dub/packages/x11-1.0.19/x11/source/x11/extensions/XI.d(3,8): Deprecation: Symbol `string` is not visible because it is privately imported
cairod 0.0.1-alpha.3+1.10.2: building configuration "static-custom-posix"...
dstats 1.0.5: building configuration "library"...
dunit 1.0.14: building configuration "library"...
painlesstraits 0.2.0: building configuration "library"...
ggplotd 1.1.4: building configuration "ggplotd-test-default"...
../../.dub/packages/color-0.0.5/color/std/experimental/normint.d(55,29): Deprecation: integral promotion not done for `-cast(ubyte)255u`, use '-transition=intpromote' switch or `-cast(int)(cast(ubyte)255u)`
../../.dub/packages/color-0.0.5/color/std/experimental/normint.d(55,29): Deprecation: integral promotion not done for `-cast(byte)127`, use '-transition=intpromote' switch or `-cast(int)(cast(byte)127)`
source/ggplotd/guide.d(439,12): Deprecation: module ggplotd.colour member `RGBA` is not accessible
source/ggplotd/geom.d(50,12): Deprecation: module ggplotd.guide member `GuideStore` is not accessible
source/ggplotd/ggplotd.d(520,12): Deprecation: module ggplotd.legend member `Legend` is not accessible

It usually times out after one hour or so, i.e. when Google terminate the GCE runners.

Seen here: https://ci.dlang.io/blue/organizations/jenkins/dlang-org%2Fdmd/detail/PR-6676/11/pipeline (but on many other PRs too)

[wilzbach]

This is a bug introduced in 6676.