Bug 1210157 - Add Python 3 support to mozboot Android toolchain bootstrap r=nalexander

Support installing the android development toolchain with Python 3 as well as
Python 2.7.

Depends on D39361

Differential Revision: https://phabricator.services.mozilla.com/D39362

--HG--
extra : moz-landing-system : lando

python/mozboot/mozboot/android.py

@@ -280,7 +280,7 @@ def ensure_android_packages(sdkmanager_tool, packages=None, no_interactive=False
 
     # Emulate yes.  For a discussion of passing input to check_output,
     # see https://stackoverflow.com/q/10103551.
-    yes = '\n'.join(['y']*100)
+    yes = '\n'.join(['y']*100).encode("UTF-8")
     proc = subprocess.Popen(args,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT,