Message 281131 - Python tracker

Here's my try: force UTF-8 on Android as explained in msg281110. sys.getfilesystemencoding() is already UTF-8 since issue22747.

Testing:
1. Starting up time 0.18~0.19s => 0.11~0.12s, on Android 6.0, ASUS ZE500KL (Qualcomm MSM8916 QuadCore 1.2GHz)
2. test_site passes