Use Aer from release for 3.9 test jobs (qiskit-community#553)

* Use Aer from release for 3.9 test jobs

In qiskit-community#505 we added jobs for Python 3.9, but because there was no released
Aer version that supported 3.9 yet to run tests we had to rely on
building aer from source in test jobs to test that things worked as
expected in CI. Now that Aer 0.7.3 has been released this included
support for python 3.9, so we now don't need to rely on building aer
from source in CI. This commit removes the job configuration to build
Aer from source in the 3.9 jobs (both in the tox configuration and
github actions config).

* Remove unecessary macOS job definition branch for 3.9

(cherry picked from commit 9fd0edc)

.github/workflows/main.yml

@@ -31,10 +31,6 @@ jobs:
         run: python -m pip install -U tox setuptools virtualenv wheel
       - name: Install and Run Tests
         run: tox -e py
-        if: matrix.python-version != '3.9'
-      - name: Install and Run Tests
-        run: tox -e py39
-        if: matrix.python-version == '3.9'
 
   tests-macos:
     name: tests-python${{ matrix.python-version }}-${{ matrix.os }}
@@ -62,10 +58,6 @@ jobs:
         run: python -m pip install -U tox setuptools virtualenv wheel cvxopt
       - name: Install and Run Tests
         run: tox --sitepackages -e py
-        if: matrix.python-version != '3.9'
-      - name: Install and Run Tests
-        run: tox --sitepackages -e py39
-        if: matrix.python-version == '3.9'
 
   tests-no-opt:
     name: tests-python3.8-no-optional-dependencies
@@ -98,8 +90,7 @@ jobs:
     runs-on: windows-latest
     strategy:
       matrix:
-        # TODO: Add 3.9 to the list after aer 0.8.0 release
-        python-version: [3.6, 3.7, 3.8]
+        python-version: [3.6, 3.7, 3.8, 3.9]
     steps:
       - uses: actions/checkout@v2
       - name: Add msbuild to PATH

requirements-dev.txt

@@ -1,6 +1,6 @@
 pylint==2.4.4
 pycodestyle
-qiskit-aer>=0.3.0;python_version<'3.9'
+qiskit-aer>=0.3.0
 scikit-learn>=0.17
 Sphinx>=2.1
 sphinx-rtd-theme>=0.4.0

tox.ini

@@ -20,15 +20,6 @@ commands =
     pip install -c constraints.txt cvxpy<1.1.8
     pip check
     stestr run {posargs}
-# Remove after qiskit-aer 0.8.0 release:
-[testenv:py39]
-commands =
-    pip install -U -c constraints.txt git+https://github.com/Qiskit/qiskit-terra.git@stable/0.16
-    pip install -U -c constraints.txt git+https://github.com/Qiskit/qiskit-aer.git
-    pip install -U -c constraints.txt -r{toxinidir}/requirements-dev.txt
-    pip install -c constraints.txt cvxpy<1.1.8
-    pip check
-    stestr run {posargs}
 
 [testenv:no-opt]
 deps =