fix: Fix build in Python 3

Since Python 3 does not have a separate "unicode" type, we create an
alias to the "str" type for compatibility with Python 2.  We do a type
check against "str" or "unicode" when parsing JSON to locate a node
binary in get_node_binary.

Closes #3102

Change-Id: Ib01fda64865052eed64e35b7856a8c392a319144

Author: joeyparrish

build/shakaBuildHelpers.py

@@ -32,6 +32,11 @@
 import sys
 import time
 
+# Python 3 no longer has a separate unicode type.  For type-checking done in
+# get_node_binary, create an alias to the str type.
+if sys.version_info[0] == 3:
+  unicode = str
+
 
 def _node_modules_last_update_path():
   return os.path.join(get_source_base(), 'node_modules', '.last_update')