How can I build a python project with osx environment on travis : <p>I am trying to build osx support for a project on Travis. The problem is osx don't ship python virtualenv natively. <a href="https://github.com/travis-ci/travis-ci/issues/2312" rel="noreferrer">Here</a> is the issue for that. I have gone through that issue and modified my travis file accordingly. Still my builds are failing with osx. <a href="https://travis-ci.org/shibasisp/python-casacore/builds/256336916" rel="noreferrer">Here</a> is a travis build link.
Here is my travis.yml file</p>

<pre><code>language: python
matrix:
    include:
        # Use the built in venv for linux builds
        - os: linux
          sudo: required
          python: "2.7"
          dist: trusty

        - os: linux
          sudo: required
          python: "3.5"
          dist: trusty

        - os: linux
          sudo: required
          python: "3.6"
          dist: trusty

        # Use generic language for osx
        - os: osx
          language: generic
          python: "2.7"

        - os: osx
          language: generic
          python: "3.5"

        - os: osx
          language: generic
          python: "3.6"

before_install:
 - .travis/before_install.sh
 - mkdir $HOME/data
 - echo $PWD
 - cd $HOME/data &amp;&amp; wget ftp://ftp.astron.nl/outgoing/Measures/WSRT_Measures.ztar &amp;&amp; tar xf WSRT_Measures.ztar &amp;&amp; cd -
 - echo $PWD
install:
 - export PATH="$HOME/miniconda/bin:$PATH"
 - source activate testenv
 - export CPATH="$HOME/miniconda/envs/testenv/include:$CPATH"
 - echo $CPATH
 - python setup.py develop
 - pip install -r tests/requirements.txt
 - pip install coveralls travis-sphinx
script:
 - nosetests --with-coverage
 - travis-sphinx --nowarn -s doc build
</code></pre>

<p>and Here is my before_install.sh file.</p>

<pre><code>set -e
set -v

if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; fi
if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then 
    if [[ "$TRAVIS_PYTHON_VERSION" == "2.7" ]]; then
        brew install python;
        virtualenv venv -p python;
        source venv/bin/activate;
    else
        brew install python3;
        virtualenv venv -p python3;
        source venv/bin/activate;
    fi
fi


if [ "$TRAVIS_OS_NAME" = linux ]; then
    sudo apt-get update
    MINICONDAVERSION="Linux"
else
    MINICONDAVERSION="MacOSX"
fi

if [[ "$TRAVIS_PYTHON_VERSION" == "2.7" ]]; then
  wget https://repo.continuum.io/miniconda/Miniconda2-latest-$MINICONDAVERSION-x86_64.sh -O miniconda.sh;
else
  wget https://repo.continuum.io/miniconda/Miniconda3-latest-$MINICONDAVERSION-x86_64.sh -O miniconda.sh;
  fi

bash miniconda.sh -b -p $HOME/miniconda
export PATH="$HOME/miniconda/bin:$PATH"
hash -r
conda config --set always_yes yes --set changeps1 no
conda update -q conda
conda config --add channels conda-forge
# Useful for debugging any issues with conda
conda info -a
which python
conda create -q -n testenv python=$TRAVIS_PYTHON_VERSION casacore=2.3.0

echo "measures.directory: /home/travis/data" &gt; $HOME/.casarc
</code></pre>

<p>It states the following error when I tried to build a conda environment.</p>

<pre><code>CondaValueError: invalid package specification: python=
</code></pre>
