Depend on specific version of python3.x-venv

This is due to mitigating effects from Debian bug 970810

See also GH-309

debian/control

@@ -20,7 +20,7 @@ Rules-Requires-Root: no
 Package: dh-virtualenv
 Architecture: all
 Depends: ${python3:Depends}, ${perl:Depends}, ${misc:Depends}, ${sphinxdoc:Depends},
- virtualenv | python3-virtualenv (>= 1.7) | python3-venv
+ virtualenv | python3-virtualenv (>= 1.7) | python${pyversion}-venv
 Built-Using: ${sphinxdoc:Built-Using}
 Description: wrap and build Python packages using virtualenv
  This package provides a dh sequencer that helps you to deploy your

debian/rules

@@ -5,6 +5,8 @@ ifeq (,$(findstring nodoc, $(DEB_BUILD_OPTIONS)))
 	DH_ARGS += --with sphinxdoc
 endif
 
+PYTHON_VERSION := $(shell python3 -c 'import sys; print("%s.%s" % sys.version_info[:2])')
+
 %:
 	dh $@ --buildsystem=pybuild --with python3 $(DH_ARGS)
 
@@ -18,6 +20,9 @@ override_dh_auto_build:
 	rst2man doc/dh_virtualenv.1.rst >doc/dh_virtualenv.1
 	dh_auto_build
 
+override_dh_gencontrol:
+	dh_gencontrol -- -Vpyversion=$(PYTHON_VERSION)
+
 ifeq (,$(findstring nodoc, $(DEB_BUILD_OPTIONS)))
 override_dh_installdocs:
 	python3 setup.py build_sphinx