Make install-sysroot work with Python 3

Tested: python3 src/build/linux/sysroot_scripts/install-sysroot.py --arch=x86
Bug: 941669
Change-Id: I23ad9c9e9e03df4d54e0961432a1cc11d5cce41a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1742194
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Auto-Submit: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685276}

build/linux/sysroot_scripts/install-sysroot.py

@@ -29,7 +29,12 @@ import re
 import shutil
 import subprocess
 import sys
-import urllib2
+try:
+    # For Python 3.0 and later
+    from urllib.request import urlopen
+except ImportError:
+    # Fall back to Python 2's urllib2
+    from urllib2 import urlopen
 
 SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
 
@@ -135,7 +140,7 @@ def InstallSysroot(target_platform, target_arch):
   sys.stderr.flush()
   for _ in range(3):
     try:
-      response = urllib2.urlopen(url)
+      response = urlopen(url)
       with open(tarball, "wb") as f:
         f.write(response.read())
       break