[gn] Paper over Py3 urllib2 incompatibility in gn/get.py

[merge_guards_bot]

Unit tests: pass. 62112 tests passed, 0 failed and 808 were skipped.

clang-tidy: pass.

clang-format: pass.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

[thakis]

llvm/utils/gn/get.py

12

Maybe try the py3 way first and then import the py2 as replacement, and move the script to use the py3 name.

llvm/utils/gn/get.py

 #!/usr/bin/env python
 """Downloads a prebuilt gn binary to a place where gn.py can find it."""
 
 from __future__ import print_function
 
 import io
 import os
-import urllib2
+try:
+    # In Python 3, we need the module urllib.reqest. In Python 2, this
+    # functionality was in the urllib2 module.
+    from urllib import request as urllib_request
+except ImportError:
+    import urllib2 as urllib_request
 import sys
 import zipfile
 
 
 def download_and_unpack(url, output_dir, gn):
     """Download an archive from url and extract gn from it into output_dir."""
     print('downloading %s ...' % url, end='')
     sys.stdout.flush()
-    data = urllib2.urlopen(url).read()
+    data = urllib_request.urlopen(url).read()
     print(' done')
     zipfile.ZipFile(io.BytesIO(data)).extract(gn, path=output_dir)
 
 
 def set_executable_bit(path):
     mode = os.stat(path).st_mode
     mode |= (mode & 0o444) >> 2 # Copy R bits to X.
     os.chmod(path, mode) # No-op on Windows.