Drop py2.7 build tests

Author: philippjfr

.github/workflows/build.yml

@@ -16,7 +16,7 @@ jobs:
         shell: bash -l {0}
     env:
       CHANS_DEV: "-c pyviz/label/dev -c bokeh"
-      PKG_TEST_PYTHON: "--test-python=py37 --test-python=py27"
+      PKG_TEST_PYTHON: "--test-python=py37"
       PYTHON_VERSION: "3.7"
       CHANS: "-c pyviz"
       MPLBACKEND: "Agg"
@@ -58,7 +58,7 @@ jobs:
         shell: bash -l {0}
     env:
       CHANS_DEV: "-c pyviz/label/dev -c bokeh"
-      PKG_TEST_PYTHON: "--test-python=py37 --test-python=py27"
+      PKG_TEST_PYTHON: "--test-python=py37"
       PYTHON_VERSION: "3.7"
       CHANS: "-c pyviz"
       MPLBACKEND: "Agg"
@@ -75,6 +75,7 @@ jobs:
       - uses: conda-incubator/setup-miniconda@v2
         with:
           miniconda-version: "latest"
+          python-version: 3.8
       - name: Fetch unshallow
         run: git fetch --prune --tags --unshallow -f
       - name: conda setup