1）change to parallel mode on python coverage run (#18594)

2）add pip install coverage in Dockerfile.tmp
test=develop

cmake/generic.cmake

@@ -728,7 +728,7 @@ function(py_test TARGET_NAME)
                FLAGS_cpu_deterministic=true FLAGS_limit_of_tmp_allocation=4294967296  # 4G
                PYTHONPATH=${PADDLE_BINARY_DIR}/python ${py_test_ENVS}
                COVERAGE_FILE=${PADDLE_BINARY_DIR}/python-coverage.data
-               ${PYTHON_EXECUTABLE} -m coverage run -a --branch ${py_test_SRCS} ${py_test_ARGS}
+               ${PYTHON_EXECUTABLE} -m coverage run --branch -p ${py_test_SRCS} ${py_test_ARGS}
                WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
     else()
       add_test(NAME ${TARGET_NAME}

paddle/scripts/Dockerfile.tmp

@@ -138,6 +138,12 @@ RUN pip --no-cache-dir install requests==2.9.2 numpy protobuf \
     recordio matplotlib==2.2.3 rarfile scipy Pillow \
     nltk graphviz six funcsigs pyyaml decorator prettytable
 
+# for coverage
+RUN pip3 --no-cache-dir install coverage
+RUN pip3.6 --no-cache-dir install coverage
+RUN pip3.7 --no-cache-dir install coverage
+RUN pip --no-cache-dir install coverage
+
 # To fix https://github.com/PaddlePaddle/Paddle/issues/1954, we use
 # the solution in https://urllib3.readthedocs.io/en/latest/user-guide.html#ssl-py2
 RUN apt-get install -y libssl-dev libffi-dev && apt-get clean -y

python/paddle/fluid/tests/unittests/CMakeLists.txt

@@ -79,7 +79,7 @@ function(py_test_modules TARGET_NAME)
       add_test(NAME ${TARGET_NAME}
           COMMAND ${CMAKE_COMMAND} -E env PYTHONPATH=${PADDLE_BINARY_DIR}/python ${py_test_modules_ENVS}
           COVERAGE_FILE=${PADDLE_BINARY_DIR}/python-coverage.data
-          ${PYTHON_EXECUTABLE} -m coverage run -a --branch ${PADDLE_SOURCE_DIR}/tools/test_runner.py ${py_test_modules_MODULES}
+          ${PYTHON_EXECUTABLE} -m coverage run --branch -p ${PADDLE_SOURCE_DIR}/tools/test_runner.py ${py_test_modules_MODULES}
           WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
     else()
       add_test(NAME ${TARGET_NAME}