[Python3] Make update-checkout work with Python 2 & 3 (#33081)

* Python3 compatibility for Benchmarks

Three issues addressed here:

1. Dependency on dictionary iteration order

 CharacterProperties.swift.gyb iterated a dictionary to produce its output.
 Changed this to a list of tuples to ensure the order is predictable.

2. Python3 `map` returns an iterator, not a list

 Changed a bunch of `map` calls to `list(map(...))` to ensure the result is a list

3. Python3 `int()` expects a string, won't accept a list of characters

 Added a concatenation step that is effectively a no-op on Python2

* Make update-checkout work with Python3

Python3 doesn't like to pickle local functions, so make the multiprocessing
initialization function be global.

Python3 multiprocessing also seems to require conditional execution of the
top-level code.  TBH, I'm not entirely sure why Python 2 didn't need this.

* Adjust whitespace per python-lint

Author: tbkka

utils/update-checkout

@@ -4,12 +4,14 @@ import sys
 
 import update_checkout
 
-# The internal Windows implementation tries to import the current module using
-# sys.modules[__name__]. This file (called 'update-checkout') is not a valid
-# Python module name, as it contains a '-' and doesn't end with '.py'. This
-# results in errors running update-checkout on Windows:'ImportError: No module
-# named update-checkout'.
-# As such, we need to manually set sys.modules[__name__] to a valid module
-# identifier to work around these errors.
-sys.modules[__name__] = sys.modules['update_checkout']
-update_checkout.main()
+if __name__ == '__main__':
+    # The internal Windows implementation tries to import the current module using
+    # sys.modules[__name__]. This file (called 'update-checkout') is not a valid
+    # Python module name, as it contains a '-' and doesn't end with '.py'. This
+    # results in errors running update-checkout on Windows:'ImportError: No module
+    # named update-checkout'.
+    # As such, we need to manually set sys.modules[__name__] to a valid module
+    # identifier to work around these errors.
+    sys.modules[__name__] = sys.modules['update_checkout']
+
+    update_checkout.main()

utils/update_checkout/update_checkout/update_checkout.py

@@ -29,6 +29,11 @@
 SCRIPT_DIR = os.path.dirname(SCRIPT_FILE)
 
 
+def child_init(lck):
+    global lock
+    lock = lck
+
+
 def run_parallel(fn, pool_args, n_processes=0):
     """Function used to run a given closure in parallel.
 
@@ -37,17 +42,13 @@ def run_parallel(fn, pool_args, n_processes=0):
     parallel implementation.
     """
 
-    def init(lck):
-        global lock
-        lock = lck
-
     if n_processes == 0:
         n_processes = cpu_count() * 2
 
     lk = Lock()
     print("Running ``%s`` with up to %d processes." %
           (fn.__name__, n_processes))
-    pool = Pool(processes=n_processes, initializer=init, initargs=(lk,))
+    pool = Pool(processes=n_processes, initializer=child_init, initargs=(lk,))
     results = pool.map_async(func=fn, iterable=pool_args).get(999999)
     pool.close()
     pool.join()