Add Py39 build (#107)

* Add Py39 build

* fixups

* update multibuild

* set pip_cmd

* set pip_cmd in test_venv

Author: TomAugspurger

azure-pipelines.yml

@@ -47,6 +47,16 @@ jobs:
           PYTHON_ARCH: "x64"
           NP_BUILD_DEP: "1.17.3"
           NIGHTLY_BUILD: "true"
+        py_3.9_32:
+          PYTHON_VERSION: "3.9"
+          PYTHON_ARCH: "x86"
+          NP_BUILD_DEP: "1.19.3"
+          NIGHTLY_BUILD: "true"
+        py_3.9_64:
+          PYTHON_VERSION: "3.9"
+          PYTHON_ARCH: "x64"
+          NP_BUILD_DEP: "1.19.3"
+          NIGHTLY_BUILD: "true"
 
   - template: azure/posix.yml
     parameters:
@@ -76,6 +86,16 @@ jobs:
           MB_PYTHON_VERSION: "3.8"
           NP_BUILD_DEP: "numpy==1.17.3"
           NIGHTLY_BUILD: "true"
+        py_3.9_32:
+          MB_PYTHON_VERSION: "3.9"
+          PLAT: "i686"
+          NP_BUILD_DEP: "numpy==1.19.3"
+          NIGHTLY_BUILD: "true"
+        py_3.9_64:
+          MB_PYTHON_VERSION: "3.9"
+          NP_BUILD_DEP: "numpy==1.19.3"
+          NIGHTLY_BUILD: "true"
+
 
   - template: azure/posix.yml
     parameters:
@@ -93,3 +113,7 @@ jobs:
           MB_PYTHON_VERSION: "3.8"
           NP_BUILD_DEP: "numpy==1.17.3"
           NIGHTLY_BUILD: "true"
+        py_3.9_64:
+          MB_PYTHON_VERSION: "3.9"
+          NP_BUILD_DEP: "numpy==1.19.3"
+          NIGHTLY_BUILD: "true"

extra_functions.sh

@@ -12,6 +12,8 @@ function setup_test_venv {
         # Note: the idiom "python -m pip install ..." is necessary to upgrade
         # pip itself on Windows. Otherwise one would get a permission error on
         # pip.exe.
+        PYTHON_EXE=python
+        PIP_CMD="$PYTHON_EXE -m pip"
         python -m pip install --upgrade pip wheel
         if [ "$TEST_DEPENDS" != "" ]; then
             pip install $TEST_DEPENDS
@@ -27,3 +29,7 @@ function teardown_test_venv {
         fi
     fi
 } 
+
+# Work around bug in multibuild. This is copied from NumPy-wheels
+# https://github.com/MacPython/numpy-wheels/blob/34c2cdaca98d020081f5d03983d1c78b3b2a828c/extra_functions.sh#L50
+if [ ! -o PIP_CMD ]; then PIP_CMD="$PYTHON_EXE -m pip"; fi