Update python dependencies

Change-Id: Ic1ba3152160e9255d14ae66881e452a99930b0d8
diff --git a/ndn-tools/debian/control b/ndn-tools/debian/control
index ed91ede..94a7f3d 100644
--- a/ndn-tools/debian/control
+++ b/ndn-tools/debian/control
@@ -1,13 +1,12 @@
 Source: ndn-tools
 Priority: extra
 Maintainer: Alexander Afanasyev <alexander.afanasyev@ucla.edu>
-Build-Depends: debhelper (>= 8.0.0),
- debhelper (>= 9.20160709),
- python3 (>= 3.5.0),
+Build-Depends: debhelper (>= 9.20160709),
+ python3 (>= 3.6.0),
  pkg-config (>= 0.26),
  libpcap-dev,
- python3-sphinx,
  libndn-cxx-dev (>= 0.8.0),
+ python3-sphinx (>= 1.6.0),
  git
 Standards-Version: 4.5.0
 Section: net