do not use conda for tests

.travis.yml

@@ -18,34 +18,21 @@ matrix:
       env: SPHINX_VERSION=1.5
     - python: "3.7"
       env: SPHINX_VERSION=1.6
+apt:
+    packages:
+        - matplotlib
+        - pandoc
 install:
-  # We do this conditionally because it saves us some downloading if the
-  # version is the same.
-  - if [[ "$TRAVIS_PYTHON_VERSION" == "2.7" ]]; then
-      NUMPY="numpy>=1.15";
-      wget https://repo.continuum.io/miniconda/Miniconda2-latest-Linux-x86_64.sh -O miniconda.sh;
-    else
-      wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh;
-    fi
-  - bash miniconda.sh -b -p $HOME/miniconda
-  - export PATH="$HOME/miniconda/bin:$PATH"
-  - hash -r
-  - conda config --set always_yes yes --set changeps1 no
-  - conda update -q conda
-  # Useful for debugging any issues with conda
-  - conda info -a
-  - conda create -n test_env python=$TRAVIS_PYTHON_VERSION matplotlib pillow sphinx=$SPHINX_VERSION jupyter pandoc $NUMPY
+  - if [[]]
+  - pip install pillow sphinx=$SPHINX_VERSION jupyter
   - source activate test_env
   - if [[ $SPHINX_VERSION == "" ]]; then
-      conda uninstall --force sphinx;
-      pip install -U sphinx;
+      pip install pillow sphinx jupyter coveralls;
+    else
+      pip install pillow sphinx=$SPHINX_VERSION jupyter coveralls;
     fi
   - if [[ "$TRAVIS_PYTHON_VERSION" == "2.7" ]]; then pip install pathlib; fi
-  - conda install notebook ipykernel
-  - ipython kernel install --user
-  - pip install coveralls
   - python setup.py install
-  - conda env export -n test_env
 
 script:
   - coverage run --source=sphinx_nbexamples setup.py pytest