Migrate to python 3

Given that on most systems Python is still linked to the Python 2.7,
switch explicitly to using Python 3.

Python 2.7 was discontinued on January 1, 2020: [1].

Moreover, there is PEP recommending to use python3 in the shebang: [2].

[1] https://www.python.org/doc/sunset-python-2
[2] https://www.python.org/dev/peps/pep-0394

Change-Id: Ia4ca09e65a451868de738d3dba6f62fdd7c5e50d

Documentation/dev-bazel.txt

diff --git a/Documentation/dev-bazel.txt b/Documentation/dev-bazel.txt
index f5fcf95..7db364c 100644
--- a/Documentation/dev-bazel.txt
+++ b/Documentation/dev-bazel.txt
@@ -19,7 +19,7 @@
 
 * A Linux or macOS system (Windows is not supported at this time)
 * A JDK for Java 8|11|...
-* Python 2 or 3
+* Python 3
 * link:https://github.com/nodesource/distributions/blob/master/README.md[Node.js (including npm),role=external,window=_blank]
 * Bower (`npm install -g bower`)
 * link:https://docs.bazel.build/versions/master/install.html[Bazel,role=external,window=_blank] -launched with