diff --git a/.travis.yml b/.travis.yml
index c6949b8..4896a58 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,11 +1,23 @@
-sudo: false
+sudo: required
 
-language: python
+language: generic
 
-python:
-  - "2.7"
-  - "3.6"
+services:
+  - docker
 
-install: pip install tox-travis
+before_install:
+  - travis_retry sudo apt update -qq
+  - travis_retry sudo apt install -qq --no-install-recommends python2.7 python3
+  - sudo pip install tox>=2.0
+  # https://github.com/travis-ci/travis-ci/issues/6069#issuecomment-266546552
+  - git remote set-branches --add origin master
+  - git fetch
 
-script: tox
+before_script:
+  # we want to fail fast on tox errors without having to `docker build` first
+  - tox
+
+script:
+  # simply makes sure the Docker image builds and run
+  - docker build --tag=buildozer .
+  - docker run buildozer --version
diff --git a/Dockerfile b/Dockerfile
index 36dacde..1748268 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,9 +2,6 @@
 # Build with:
 # docker build --tag=buildozer .
 # 
-# if you want to use bleeding edge/current version from git, instead from pypi, then use
-# docker build --tag=buildozer --build-arg git=true .
-#
 # In order to give the container access to your current working directory
 # it must be mounted using the --volume option.
 # Run with (e.g. `buildozer --version`):
@@ -13,17 +10,13 @@
 # docker run --volume "$(pwd)":/home/user/hostcwd --entrypoint /bin/bash -it --rm buildozer
 
 FROM ubuntu:18.04
-ARG git
 
-ENV BDOZER_REQ=${git:+"/src"}
-ENV BDOZER_REQ=${BDOZER_REQ:-"buildozer"}
 ENV USER="user"
 ENV HOME_DIR="/home/${USER}"
 ENV WORK_DIR="${HOME_DIR}/hostcwd" \
+    SRC_DIR="${HOME_DIR}/src" \
     PATH="${HOME_DIR}/.local/bin:${PATH}"
 
-COPY . /src
-
 # configures locale
 RUN apt update -qq > /dev/null && \
     apt install -qq --yes --no-install-recommends \
@@ -35,14 +28,14 @@ ENV LANG="en_US.UTF-8" \
 
 # installs system dependencies (required to setup all the tools)
 RUN apt install -qq --yes --no-install-recommends \
-    sudo python-pip python-setuptools file
+    sudo python3-pip python3-setuptools file
 
 # https://buildozer.readthedocs.io/en/latest/installation.html#android-on-ubuntu-18-04-64bit
 RUN dpkg --add-architecture i386 && apt update -qq > /dev/null && \
 	apt install -qq --yes --no-install-recommends \
 	build-essential ccache git libncurses5:i386 libstdc++6:i386 libgtk2.0-0:i386 \
-	libpangox-1.0-0:i386 libpangoxft-1.0-0:i386 libidn11:i386 python2.7 \
-	python2.7-dev openjdk-8-jdk unzip zlib1g-dev zlib1g:i386
+	libpangox-1.0-0:i386 libpangoxft-1.0-0:i386 libidn11:i386 python2.7 python3 \
+	python3-dev openjdk-8-jdk unzip zlib1g-dev zlib1g:i386
 
 # prepares non root env
 RUN useradd --create-home --shell /bin/bash ${USER}
@@ -52,15 +45,9 @@ RUN echo "%sudo ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers
 
 USER ${USER}
 WORKDIR ${WORK_DIR}
+COPY --chown=user:user . ${SRC_DIR}
 
 # installs buildozer and dependencies
-RUN pip install --user Cython==0.25.2 $BDOZER_REQ
-
-# calling buildozer adb command should trigger SDK/NDK first install and update
-# but it requires a buildozer.spec file
-RUN cd /tmp/ && buildozer init && buildozer android adb -- version && cd -
-# fixes source and target JDK version, refs https://github.com/kivy/buildozer/issues/625
-RUN sed s/'name="java.source" value="1.5"'/'name="java.source" value="7"'/ -i ${HOME_DIR}/.buildozer/android/platform/android-sdk-20/tools/ant/build.xml
-RUN sed s/'name="java.target" value="1.5"'/'name="java.target" value="7"'/ -i ${HOME_DIR}/.buildozer/android/platform/android-sdk-20/tools/ant/build.xml
+RUN pip3 install --user Cython==0.28.6 ${SRC_DIR}
 
 ENTRYPOINT ["buildozer"]
diff --git a/buildozer/__init__.py b/buildozer/__init__.py
index 4dea760..3b1f1cc 100644
--- a/buildozer/__init__.py
+++ b/buildozer/__init__.py
@@ -510,10 +510,12 @@ class Buildozer(object):
             exit(1)
 
         # did we already installed the libs ?
-        if exists(self.applibs_dir) and \
-           self.state.get('cache.applibs', '') == requirements:
-                self.debug('Application requirements already installed, pass')
-                return
+        if (
+            exists(self.applibs_dir) and
+            self.state.get('cache.applibs', '') == requirements
+        ):
+            self.debug('Application requirements already installed, pass')
+            return
 
         # recreate applibs
         self.rmdir(self.applibs_dir)
diff --git a/tox.ini b/tox.ini
index 7598029..3008490 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = pep8,py27,py36
+envlist = pep8,py27,py3
 
 [testenv]
 deps = mock