Provide Upgrade Tool for Discovering Major Changes

[rcuza]

While upgrading to v2.0.0, I discovered that the removal of the provides= field in python_library fails one at a time. In other words, running ./pants filedeps :: will cause an exception message for one of the broken target definitions with a provides= field. Once that is fixed, the command will fail in the exact same way on the next target with a provides= field.

Story

As a person upgrading pants I would like to run a command that looks at my monorepo and reports on all the work that needs to be done to upgrade to the next version.

Details of Example

Engine traceback:
  in select
  in pants.backend.project_info.filedeps.file_deps
  in pants.engine.internals.graph.resolve_targets
  in pants.engine.internals.graph.resolve_unexpanded_targets
  in pants.engine.internals.graph.resolve_target (pycb/src/python/jupyter_stubber)
Traceback (most recent call last):
  File "/Users/myacct/.cache/pants/setup/bootstrap-Darwin-x86_64/2.0.0rc0_py36/lib/python3.6/site-packages/pants/engine/internals/native.py", line 69, in generator_send
    res = func.send(arg)
  File "/Users/myacct/.cache/pants/setup/bootstrap-Darwin-x86_64/2.0.0rc0_py36/lib/python3.6/site-packages/pants/engine/internals/graph.py", line 142, in resolve_target
    target = target_type(target_adaptor.kwargs, address=address, union_membership=union_membership)
  File "/Users/myacct/.cache/pants/setup/bootstrap-Darwin-x86_64/2.0.0rc0_py36/lib/python3.6/site-packages/pants/util/meta.py", line 182, in new_init
    prev_init(self, *args, **kwargs)
  File "/Users/myacct/.cache/pants/setup/bootstrap-Darwin-x86_64/2.0.0rc0_py36/lib/python3.6/site-packages/pants/engine/target.py", line 287, in __init__
    f"Unrecognized field `{alias}={value}` in target {address}. Valid fields for "
pants.engine.target.InvalidFieldException: Unrecognized field `provides=jupyter_stubber` in target pycb/src/python/jupyter_stubber. Valid fields for the target type `python_library`: ['compatibility', 'dependencies', 'description', 'sources', 'tags'].

[Eric-Arellano]

Closed by #10970