Port patches from 1.0.0 branch (#5336)

* Remove f-string, since it's not supported by Python 3.5 (#5330)

* Remove f-string, since it's not supported by Python 3.5

* Add Python 3.5 to CI, to ensure compatibility

* Remove duplicated matplotlib

* Show deprecation notice for Python 3.5

* Fix lint

* Fix lint

* Fix a unit test that mistook MINOR ver for PATCH ver

* Enforce only major version in JSON model schema

* Bump version to 1.1.0-SNAPSHOT

tests/ci_build/Dockerfile.cpu

@@ -3,6 +3,7 @@ ARG CMAKE_VERSION=3.12
 
 # Environment
 ENV DEBIAN_FRONTEND noninteractive
+SHELL ["/bin/bash", "-c"]   # Use Bash as shell
 
 # Install all basic requirements
 RUN \
@@ -19,10 +20,16 @@ ENV PATH=/opt/python/bin:$PATH
 
 ENV GOSU_VERSION 1.10
 
-# Install Python packages
+# Create new Conda environment with Python 3.5
+RUN conda create -n py35 python=3.5 && \
+    source activate py35 && \
+    pip install numpy pytest scipy scikit-learn pandas matplotlib wheel kubernetes urllib3 graphviz && \
+    source deactivate
+
+# Install Python packages in default env
 RUN \
     pip install pyyaml cpplint pylint astroid sphinx numpy scipy pandas matplotlib sh \
-    		recommonmark guzzle_sphinx_theme mock breathe matplotlib graphviz \
+    		recommonmark guzzle_sphinx_theme mock breathe graphviz \
 		pytest scikit-learn wheel kubernetes urllib3 jsonschema boto3 && \
     pip install https://h2o-release.s3.amazonaws.com/datatable/stable/datatable-0.7.0/datatable-0.7.0-cp37-cp37m-linux_x86_64.whl && \
     pip install "dask[complete]"

tests/ci_build/test_python.sh

@@ -5,31 +5,35 @@ set -x
 suite=$1
 
 # Install XGBoost Python package
-wheel_found=0
-for file in python-package/dist/*.whl
-do
-  if [ -e "${file}" ]
+function install_xgboost {
+  wheel_found=0
+  for file in python-package/dist/*.whl
+  do
+    if [ -e "${file}" ]
+    then
+      pip install --user "${file}"
+      wheel_found=1
+      break  # need just one
+    fi
+  done
+  if [ "$wheel_found" -eq 0 ]
   then
-    pip install --user "${file}"
-    wheel_found=1
-    break  # need just one
+    pushd .
+    cd python-package
+    python setup.py install --user
+    popd
   fi
-done
-if [ "$wheel_found" -eq 0 ]
-then
-  pushd .
-  cd python-package
-  python setup.py install --user
-  popd
-fi
+}
 
 # Run specified test suite
 case "$suite" in
   gpu)
+    install_xgboost
     pytest -v -s --fulltrace -m "not mgpu" tests/python-gpu
     ;;
 
   mgpu)
+    install_xgboost
     pytest -v -s --fulltrace -m "mgpu" tests/python-gpu
     cd tests/distributed
     ./runtests-gpu.sh
@@ -39,17 +43,25 @@ case "$suite" in
 
   cudf)
     source activate cudf_test
+    install_xgboost
     pytest -v -s --fulltrace -m "not mgpu" tests/python-gpu/test_from_columnar.py tests/python-gpu/test_from_cupy.py
     ;;
 
   cpu)
+    install_xgboost
     pytest -v -s --fulltrace tests/python
     cd tests/distributed
     ./runtests.sh
     ;;
 
+  cpu-py35)
+    source activate py35
+    install_xgboost
+    pytest -v -s --fulltrace tests/python
+    ;;
+
   *)
-    echo "Usage: $0 {gpu|mgpu|cudf|cpu}"
+    echo "Usage: $0 {gpu|mgpu|cudf|cpu|cpu-py35}"
     exit 1
     ;;
 esac