Error(s) in re-building vignettes:
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--- re-building ‘contribute.Rmd’ using rmarkdown
--- finished re-building ‘contribute.Rmd’

--- re-building ‘overview_colors.Rmd’ using rmarkdown
--- finished re-building ‘overview_colors.Rmd’

--- re-building ‘overview_shapes.Rmd’ using rmarkdown
trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Acanthuridae_Acanthurus.nigricauda.png’
Content type 'image/png' length 14714 bytes (14 KB)
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downloaded 14 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Acanthuridae_Ctenochaetus.striatus.png’
Content type 'image/png' length 18316 bytes (17 KB)
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downloaded 17 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Acanthuridae_Naso.lituratus.png’
Content type 'image/png' length 16463 bytes (16 KB)
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downloaded 16 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Acanthuridae_Naso.unicornis.png’
Content type 'image/png' length 13447 bytes (13 KB)
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downloaded 13 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Acanthuridae_Zebrasoma.scopas.png’
Content type 'image/png' length 21381 bytes (20 KB)
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downloaded 20 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Acanthuridae_Zebrasoma.velifer.png’
Content type 'image/png' length 23543 bytes (22 KB)
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downloaded 22 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Acipenseridae_Acipenser.fulvescens.png’
Content type 'image/png' length 54437 bytes (53 KB)
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downloaded 53 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Alopiidae_Alopias.vulpinus.png’
Content type 'image/png' length 11972 bytes (11 KB)
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downloaded 11 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Apogonidae_Apogon.binotatus.png’
Content type 'image/png' length 14130 bytes (13 KB)
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downloaded 13 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Atherinopsidae_Atherinella.brasiliensis.png’
Content type 'image/png' length 29108 bytes (28 KB)
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downloaded 28 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Aulostomidae_Aulostomus.chinensis.png’
Content type 'image/png' length 6758 bytes
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downloaded 6758 bytes

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Balistidae_Balistapus.undulatus.png’
Content type 'image/png' length 35965 bytes (35 KB)
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downloaded 35 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Balistidae_Odonus.niger.png’
Content type 'image/png' length 2954 bytes
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downloaded 2954 bytes

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Belonidae_Belone.belone.png’
Content type 'image/png' length 5509 bytes
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downloaded 5509 bytes

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Blenniidae_Antennablennius.adenensis.png’
Content type 'image/png' length 10511 bytes (10 KB)
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downloaded 10 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Blenniidae_Ecsenius.pulcher.png’
Content type 'image/png' length 9060 bytes
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downloaded 9060 bytes

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Blenniidae_Hypleurochilus.pseudoaequipinnis.png’
Content type 'image/png' length 13239 bytes (12 KB)
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downloaded 12 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Bothidae_Bothus.mancus.png’
Content type 'image/png' length 14923 bytes (14 KB)
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downloaded 14 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Bythitidae_Dinematichthys.iluocoeteoides.png’
Content type 'image/png' length 9296 bytes
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downloaded 9296 bytes

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Caesionidae_Caesio.cuning.png’
Content type 'image/png' length 16081 bytes (15 KB)
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downloaded 15 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Callionymidae_Callionymus.bairdi.png’
Content type 'image/png' length 8433 bytes
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downloaded 8433 bytes

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Carangidae_Caranx.melampygus.png’
Content type 'image/png' length 14122 bytes (13 KB)
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downloaded 13 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Carcharhinidae_Triaenodon.obesus.png’
Content type 'image/png' length 10541 bytes (10 KB)
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trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Centrarchidae_Lepomis.megalotis.png’
Content type 'image/png' length 20380 bytes (19 KB)
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downloaded 19 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Chaenopsidae_Acanthemblemaria.spinosa.png’
Content type 'image/png' length 7887 bytes
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trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Chaetodontidae_Chaetodon.auriga.png’
Content type 'image/png' length 14177 bytes (13 KB)
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downloaded 13 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Chaetodontidae_Chaetodon.ornatissimus.png’
Content type 'image/png' length 4324 bytes
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downloaded 4324 bytes

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Chaetodontidae_Chaetodon.plebeius.png’
Content type 'image/png' length 14644 bytes (14 KB)
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downloaded 14 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Chaetodontidae_Chaetodon.vagabundus.png’
Content type 'image/png' length 28648 bytes (27 KB)
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downloaded 27 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Channichthyidae_Chaenocephalus.aceratus.png’
Content type 'image/png' length 11510 bytes (11 KB)
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downloaded 11 KB

trying URL ‘https://raw.githubusercontent.com/simonjbrandl/fishape/master/shapes/Characidae_Colossoma.macropomum.png’
Content type 'image/png' length 50104 bytes (48 KB)
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downloaded 48 KB

Quitting from lines 23-32 (overview_shapes.Rmd) 
Error: processing vignette 'overview_shapes.Rmd' failed with diagnostics:
Internal Server Error (HTTP 500).
--- failed re-building ‘overview_shapes.Rmd’

SUMMARY: processing the following file failed:
  ‘overview_shapes.Rmd’

Error: Vignette re-building failed.
Execution halted