set opencv-python <=4.2.0.32 (#26415)

paddle/scripts/paddle_build.sh

@@ -580,7 +580,8 @@ function generate_api_spec() {
     cd ${PADDLE_ROOT}/build/.check_api_workspace
     virtualenv .${spec_kind}_env
     source .${spec_kind}_env/bin/activate
-    pip install ${PADDLE_ROOT}/build/python/dist/*whl
+    pip install -r ${PADDLE_ROOT}/python/requirements.txt
+    pip --no-cache-dir install ${PADDLE_ROOT}/build/python/dist/*whl
     spec_path=${PADDLE_ROOT}/paddle/fluid/API_${spec_kind}.spec
     python ${PADDLE_ROOT}/tools/print_signatures.py paddle > $spec_path
 

python/requirements.txt

@@ -1,3 +1,4 @@
+opencv-python<=4.2.0.32
 requests>=2.20.0
 numpy>=1.13, <=1.16.4 ; python_version<"3.5"
 numpy>=1.13 ; python_version>="3.5"