github: Fix handling of python packages.

GitHub Actions doesn't have python locations in PATH and different
runners might have different configuration for default python
location and versions.  For example, on some runners python2 might
be installed or not.

Missing PATH causes weird situations on older branches where during
one run our scripts can locate just installed flake8 and can't do
that on a different run.  But this might also create other
unpredictable issues on all branches.

It's required to use actions/setup-python@v2 in order to have
predictable version of python installed and paths correctly configured.
Due to some bugs in GHA itself it doesn't set $HOME/.local/bin into
PATH, so we have to do that manually for now in order to use '--user'.
This might be fixed later in actions/setup-python or in base runners.
We already setting it for DPDK 20.11 (I think the issue was spotted
but not fully investigated).  Moving PATH updates to a separate step
to make them more explicit and available for all steps of the job.

Unfortunately actions/setup-python@v2 also makes invisible python
packages installed from Ubuntu repositories.  Switching them to
'pip3 install'.

Fixes: 6cb2f5a ("github: Add GitHub Actions workflow.")
Reported-by: Numan Siddique <numans@ovn.org>
Acked-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

.ci/linux-prepare.sh

@@ -20,7 +20,8 @@ cd sparse
 make -j4 HAVE_LLVM= HAVE_SQLITE= install
 cd ..
 
-pip3 install --disable-pip-version-check --user flake8 hacking
+pip3 install --disable-pip-version-check --user \
+    flake8 hacking sphinx pyOpenSSL wheel setuptools
 pip3 install --user --upgrade docutils
 pip3 install --user  'meson==0.47.1'
 

.github/workflows/build-and-test.yml

@@ -8,9 +8,7 @@ jobs:
       dependencies: |
         automake libtool gcc bc libjemalloc1 libjemalloc-dev    \
         libssl-dev llvm-dev libelf-dev libnuma-dev libpcap-dev  \
-        ninja-build python3-openssl python3-pip                 \
-        python3-setuptools python3-sphinx python3-wheel         \
-        selinux-policy-dev
+        ninja-build selinux-policy-dev
       deb_dependencies: |
         linux-headers-$(uname -r) build-essential fakeroot devscripts equivs
       AFXDP:       ${{ matrix.afxdp }}
@@ -115,6 +113,16 @@ jobs:
     - name: checkout
       uses: actions/checkout@v2
 
+    - name: update PATH
+      run:  |
+        echo "$HOME/bin"        >> $GITHUB_PATH
+        echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+    - name: set up python
+      uses: actions/setup-python@v2
+      with:
+        python-version: '3.x'
+
     - name: create ci signature file for the dpdk cache key
       if:   matrix.dpdk != '' || matrix.dpdk_shared != ''
       # This will collect most of DPDK related lines, so hash will be different
@@ -151,7 +159,7 @@ jobs:
       run:  ./.ci/linux-prepare.sh
 
     - name: build
-      run:  PATH="$PATH:$HOME/bin:$HOME/.local/bin" ./.ci/linux-build.sh
+      run:  ./.ci/linux-build.sh
 
     - name: upload deb packages
       if:   matrix.deb_package != ''
@@ -194,12 +202,20 @@ jobs:
     steps:
     - name: checkout
       uses: actions/checkout@v2
+    - name: update PATH
+      run:  |
+        echo "$HOME/bin"        >> $GITHUB_PATH
+        echo "$HOME/.local/bin" >> $GITHUB_PATH
+    - name: set up python
+      uses: actions/setup-python@v2
+      with:
+        python-version: '3.x'
     - name: install dependencies
       run:  brew install automake libtool
     - name: prepare
       run:  ./.ci/osx-prepare.sh
     - name: build
-      run:  PATH="$PATH:$HOME/bin" ./.ci/osx-build.sh
+      run:  ./.ci/osx-build.sh
     - name: upload logs on failure
       if: failure()
       uses: actions/upload-artifact@v2