docker: move tests from python2 to python3

As part of the push to drop python2 support, replace any explicit python2
dependencies with python3 versions.

For centos, python2 still exists as an implicit dependency, but by adding
python3 we will be able to build even if the configure script begins to
require python 3.5+.

Tested with centos7, fedora, ubuntu, ubuntu1804, and debian 9 (amd64).
Tested under a custom configure script that requires Python 3.5+.

the travis dockerfile is also moved to using python3, which was tested
by running `make docker-test-build@travis`, which I hope is sufficient.
Signed-off-by: NJohn Snow <jsnow@redhat.com>
Message-Id: <20190923181140.7235-7-jsnow@redhat.com>
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NCleber Rosa <crosa@redhat.com>
Tested-by: NCleber Rosa <crosa@redhat.com>

tests/docker/dockerfiles/centos7.docker

@@ -25,6 +25,7 @@ ENV PACKAGES \
     nettle-devel \
     perl-Test-Harness \
     pixman-devel \
+    python3 \
     SDL-devel \
     spice-glib-devel \
     spice-server-devel \
@@ -34,4 +35,3 @@ ENV PACKAGES \
     zlib-devel
 RUN yum install -y $PACKAGES
 RUN rpm -q $PACKAGES | sort > /packages.txt
-

tests/docker/dockerfiles/debian-xtensa-cross.docker

@@ -18,7 +18,7 @@ RUN apt-get update && \
         flex \
         gettext \
         git \
-        python-minimal
+        python3-minimal
 
 ENV CPU_LIST csp dc232b dc233c
 ENV TOOLCHAIN_RELEASE 2018.02

tests/docker/dockerfiles/debian10.docker

@@ -26,7 +26,7 @@ RUN apt update && \
         git \
         pkg-config \
         psmisc \
-        python \
+        python3 \
         python3-sphinx \
         texinfo \
         $(apt-get -s build-dep qemu | egrep ^Inst | fgrep '[all]' | cut -d\  -f2)

tests/docker/dockerfiles/debian9.docker

@@ -26,7 +26,7 @@ RUN apt update && \
         git \
         pkg-config \
         psmisc \
-        python \
+        python3 \
         python3-sphinx \
         texinfo \
         $(apt-get -s build-dep qemu | egrep ^Inst | fgrep '[all]' | cut -d\  -f2)

tests/docker/dockerfiles/travis.docker

@@ -5,7 +5,7 @@ ENV LC_ALL en_US.UTF-8
 RUN sed -i "s/# deb-src/deb-src/" /etc/apt/sources.list
 RUN apt-get update
 RUN apt-get -y build-dep qemu
-RUN apt-get -y install device-tree-compiler python2.7 python-yaml dh-autoreconf gdb strace lsof net-tools gcovr
+RUN apt-get -y install device-tree-compiler python3 python3-yaml dh-autoreconf gdb strace lsof net-tools gcovr
 # Travis tools require PhantomJS / Neo4j / Maven accessible
 # in their PATH (QEMU build won't access them).
 ENV PATH /usr/local/phantomjs/bin:/usr/local/phantomjs:/usr/local/neo4j-3.2.7/bin:/usr/local/maven-3.5.2/bin:/usr/local/cmake-3.9.2/bin:/usr/local/clang-5.0.0/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

tests/docker/dockerfiles/ubuntu.docker

@@ -60,7 +60,7 @@ ENV PACKAGES flex bison \
     libvte-2.91-dev \
     libxen-dev \
     make \
-    python-yaml \
+    python3-yaml \
     python3-sphinx \
     sparse \
     texinfo \

tests/docker/dockerfiles/ubuntu1804.docker

@@ -47,7 +47,7 @@ ENV PACKAGES flex bison \
     libvte-2.91-dev \
     libxen-dev \
     make \
-    python-yaml \
+    python3-yaml \
     python3-sphinx \
     sparse \
     texinfo \