Update python dependencies

Change-Id: Ic1ba3152160e9255d14ae66881e452a99930b0d8
diff --git a/chronochat/debian/control b/chronochat/debian/control
index b20d34c..180319b 100644
--- a/chronochat/debian/control
+++ b/chronochat/debian/control
@@ -2,7 +2,7 @@
 Priority: extra
 Maintainer: Alexander Afanasyev <alexander.afanasyev@ucla.edu>
 Build-Depends: debhelper (>= 8.0.0),
- python (>= 2.7.0),
+ python3 (>= 3.6.0),
  pkg-config (>= 0.26),
  ndn-cxx-dev (>= 0.2.0),
  liblog4cxx10-dev (>= 0.10.0),