Update matplotlib install (#3443)

* Update matplotlib install

* Test commit

* Add force reinstall

* Add larger tolerance to quadpotential

* Widen tolerance to second assert

* Add comment regarding TravisCI changes

Author: canyon289

pymc3/tests/test_quadpotential.py

@@ -51,8 +51,8 @@ def test_equal_diag():
         for pot in pots:
             v_ = pot.velocity(x)
             e_ = pot.energy(x)
-            npt.assert_allclose(v_, v)
-            npt.assert_allclose(e_, e)
+            npt.assert_allclose(v_, v, rtol=1e-6)
+            npt.assert_allclose(e_, e, rtol=1e-6)
 
 
 def test_equal_dense():

scripts/create_testenv.sh

@@ -33,15 +33,16 @@ then
     fi
     source activate ${ENVNAME}
 fi
-conda install --yes numpy scipy mkl-service matplotlib
+conda install --yes numpy scipy mkl-service
 conda install --yes -c conda-forge python-graphviz
 
 pip install --upgrade pip
 
 #  Install editable using the setup.py
-pip install -e .
 
-pip install -r requirements-dev.txt
+# Travis env is unable to import cached mpl sometimes https://github.com/pymc-devs/pymc3/issues/3423
+pip install --no-cache-dir --ignore-installed -e .
+pip install --no-cache-dir --ignore-installed -r requirements-dev.txt
 
 # Install untested, non-required code (linter fails without them)
 pip install ipython ipywidgets