fix node.js server startup

Author: poke1024

mathics/layout/client.py

@@ -4,9 +4,9 @@
 # Your installation of nodejs with the following packages: mathjax-node svg2png (install them using
 # npm).
 
-# Tips for installing nodejs on OS X:
-# see https://gist.github.com/DanHerbert/9520689
-# export NODE_PATH=/your/path/to/homebrew/bin/node_modules:$NODE_PATH
+# Tips for troubleshooting:
+# https://docs.npmjs.com/resolving-eacces-permissions-errors-when-installing-packages-globally
+# export NODE_PATH=$(npm root --quiet -g)
 
 import subprocess
 from subprocess import Popen
@@ -162,7 +162,7 @@ def _create_client(self):
             server_path = os.path.join(
                 os.path.dirname(os.path.realpath(__file__)), 'server.js')
 
-            if True:
+            if False:
                 # fixes problems on Windows network drives
                 import tempfile
                 fd, copied_path = tempfile.mkstemp(suffix='js')
@@ -172,7 +172,8 @@ def _create_client(self):
                 server_path = copied_path
 
             def abort(message):
-                error_text = 'Node.js failed to startup %s:\n\n' % server_path
+                error_text = '\nNode.js failed to start Mathics server.\n'
+                    'You might need to run: npm install -g mathjax-node svg2png\n\n'
                 raise WebEngineUnavailable(error_text + message)
 
             process = Popen(
@@ -192,7 +193,7 @@ def abort(message):
                     error += '  ' + line
 
                 process.terminate()
-                abort(error + '\nPlease check Node.js modules and NODE_PATH')
+                abort(error)
 
             port = int(status[len(hello):])
         except OSError as e:

mathics/layout/server.js

@@ -1,4 +1,4 @@
-// to install: npm install mathjax-node svg2png
+// to install: npm install -g mathjax-node svg2png
 
 try {
     function server(methods) {
@@ -72,7 +72,7 @@ try {
         server.listen(0);  // pick a free port
     }
 
-    var mathjax = require("mathjax-node/lib/mj-single.js");
+    var mathjax = require("mathjax-node");
     mathjax.config({
         MathJax: {
             // traditional MathJax configuration