bokehjs' build fails on Windows with no explanation

[mattpap]

[06:10:08] Starting 'styles:compile'...
[06:10:09] Finished 'styles:compile' after 223 ms
[06:10:09] Starting 'scripts:styles'...
[06:10:09] Finished 'scripts:styles' after 60 ms
[06:10:09] Starting 'scripts:glsl'...
[06:10:09] Finished 'scripts:glsl' after 13 ms
[06:10:09] Starting 'scripts:version'...
[06:10:09] Finished 'scripts:version' after 0 ms
[06:10:09] Starting 'scripts:compile'...
[06:10:22] Finished 'scripts:compile' after 13.60 s
[06:10:22] Starting 'scripts:bundle'...
[06:10:45] Finished 'scripts:bundle' after 22.94 s
[06:10:45] Finished 'lib:build'
[06:10:45] Finished 'scripts:build'
[06:10:45] Starting 'compiler:ts'...
[06:10:46] Finished 'compiler:ts' after 1.27 s
[06:10:46] Starting 'compiler:build'...
[06:10:52] Finished 'compiler:build' after 5.30 s
[06:10:52] Starting 'examples:compile'...
null
[06:10:53] Finished 'examples:compile' after 1.43 s
null
[06:10:53] Finished 'examples:build'
[06:10:53] Starting 'pack'...
[06:10:53] Finished 'pack' after 3 ms
[06:10:53] failed: failed to run 'npm.cmd pack'
[06:10:53] failed: failed to run 'npm.cmd pack'
[06:10:53] failed: task 'top-level' failed because 'pack' failed
[06:10:53] failed: task 'top-level' failed because 'pack' failed