[v1.x] Update CI build scripts to install python 3.6 from deadsnakes …

…repo (apache#19788)

* Install python3.6 from deadsnakes repo, since 3.5 is EOL'd and get-pip.py no longer works with 3.5.

* Set symlink for python3 to point to newly installed 3.6 version.

* Setting symlink or using update-alternatives causes add-apt-repository to fail, so instead just set alias in environment to call the correct python version.

* Setup symlinks in /usr/local/bin, since it comes first in the path.

* Don't use absolute path for python3 executable, just use python3 from path.

Co-authored-by: Joe Evans <joeev@amazon.com>

ci/docker/install/ubuntu_python.sh

@@ -23,7 +23,12 @@
 set -ex
 # install libraries for mxnet's python package on ubuntu
 apt-get update || true
-apt-get install -y python-dev python3-dev virtualenv wget
+apt-get install -y software-properties-common
+add-apt-repository -y ppa:deadsnakes/ppa
+apt-get update || true
+apt-get install -y python3.6-dev virtualenv wget
+# setup symlink in /usr/local/bin to override python3 version
+ln -sf /usr/bin/python3.6 /usr/local/bin/python3
 
 # the version of the pip shipped with ubuntu may be too lower, install a recent version here
 wget -nv https://bootstrap.pypa.io/get-pip.py

ci/docker/runtime_functions.sh

@@ -517,7 +517,7 @@ build_ubuntu_cpu_cmake_debug() {
     cmake \
         -DUSE_CUDA=OFF \
         -DUSE_TVM_OP=ON \
-        -DPython3_EXECUTABLE=/usr/bin/python3 \
+        -DPython3_EXECUTABLE=python3 \
         -DUSE_MKL_IF_AVAILABLE=OFF \
         -DUSE_OPENMP=OFF \
         -DUSE_OPENCV=ON \
@@ -538,7 +538,7 @@ build_ubuntu_cpu_cmake_no_tvm_op() {
     cmake \
         -DUSE_CUDA=OFF \
         -DUSE_TVM_OP=OFF \
-        -DPython3_EXECUTABLE=/usr/bin/python3 \
+        -DPython3_EXECUTABLE=python3 \
         -DUSE_MKL_IF_AVAILABLE=OFF \
         -DUSE_OPENMP=OFF \
         -DUSE_OPENCV=ON \
@@ -874,7 +874,7 @@ build_ubuntu_gpu_cmake_mkldnn() {
         -DUSE_CUDA=1                            \
         -DUSE_CUDNN=1                           \
         -DUSE_TVM_OP=0                          \
-        -DPython3_EXECUTABLE=/usr/bin/python3   \
+        -DPython3_EXECUTABLE=python3            \
         -DUSE_MKLML_MKL=1                       \
         -DCMAKE_BUILD_TYPE=Release              \
         -DMXNET_CUDA_ARCH="$CI_CMAKE_CUDA_ARCH" \
@@ -892,8 +892,8 @@ build_ubuntu_gpu_cmake() {
         -DUSE_SIGNAL_HANDLER=ON                 \
         -DUSE_CUDA=ON                           \
         -DUSE_CUDNN=ON                          \
-        -DUSE_TVM_OP=OFF                         \
-        -DPython3_EXECUTABLE=/usr/bin/python3   \
+        -DUSE_TVM_OP=OFF                        \
+        -DPython3_EXECUTABLE=python3            \
         -DUSE_MKL_IF_AVAILABLE=OFF              \
         -DUSE_MKLML_MKL=OFF                     \
         -DUSE_MKLDNN=OFF                        \
@@ -915,8 +915,8 @@ build_ubuntu_gpu_cmake_no_rtc() {
         -DUSE_SIGNAL_HANDLER=ON                 \
         -DUSE_CUDA=ON                           \
         -DUSE_CUDNN=ON                          \
-        -DUSE_TVM_OP=OFF                         \
-        -DPython3_EXECUTABLE=/usr/bin/python3   \
+        -DUSE_TVM_OP=OFF                        \
+        -DPython3_EXECUTABLE=python3            \
         -DUSE_MKL_IF_AVAILABLE=OFF              \
         -DUSE_MKLML_MKL=OFF                     \
         -DUSE_MKLDNN=ON                         \
@@ -956,8 +956,8 @@ build_ubuntu_gpu_large_tensor() {
         -DUSE_SIGNAL_HANDLER=ON                 \
         -DUSE_CUDA=ON                           \
         -DUSE_CUDNN=ON                          \
-        -DUSE_TVM_OP=OFF                         \
-        -DPython3_EXECUTABLE=/usr/bin/python3   \
+        -DUSE_TVM_OP=OFF                        \
+        -DPython3_EXECUTABLE=python3            \
         -DUSE_MKL_IF_AVAILABLE=OFF              \
         -DUSE_MKLML_MKL=OFF                     \
         -DUSE_MKLDNN=OFF                        \