* [CodeStyle][py2][U004] unecessary explicit `object` inheritance in class definition

* fix an increment

* update config

* re-blacken python code

* temporarily disable date and diff_py_file

* skip a format

* [CodeStyle] remove all future import

* revert test_error.py

* restore future import in example code

* add static_only for static api

* addd static_only for class init

* remove static_only for default_main_program

* remove creater_parameter & startup_program

* remove failed apis

* revert py_func import

* remove global scope

* remove some api

* remove cuda pinned place

As the title

This PR enhances error messages of several API/OPs:

ParallelExecutor (python && C++)
Executor (python && C++)
StaticRNN (python)
IfElse (python)
cond (python)
split_lod_tensor (python && C++)

* fix fluid.data
test=document_fix

* fix doc batch dim
test=document_fix

* polish executor doc
test=develop

* remove compile from PE
test=develop

* update exe.run

* fix code bug
test=develop

test=develop

* reset drop local scope counter
test=develop

* polish doc
test=develop

* updata parallel executor doc
test=develop

* update API.spec
test=develop

* polish code
test=develop

test=develop

test=develop

* unified PE and compiler
test=develop

* Polish code
test=develop

* unified PE and compiler
test=develop

* Polish code
test=develop

* Unified ParallelExecutor and Compiler

test=develop

* Unified ParallelExecutor and Compiler

test=develop

test=develop

test=develop

test=develop

test=develop