Variable length tuples not working in 1.8.0

[tlambert03]

Checks

• I added a descriptive title to this issue
• I have searched (google, github) for similar issues and couldn't find anything
• I have read and followed the docs and still think this is a bug

Bug

It wasn't clear to me from the description of the breaking changes described in 1.8.0 whether it is expected that variable length tuples should now be handled differently, but I'm seeing something similar to #2132 when nesting generics inside of a variable length tuple:

from typing import Tuple
from pydantic import BaseModel

# works
class A(BaseModel):
	t: Tuple[Tuple[int]] = ()

# works
class B(BaseModel):
	t: Tuple[Tuple[int, ...]] = ()

# fails
class C(BaseModel):
	t: Tuple[Tuple[int], ...] = ()

TypeError                                 Traceback (most recent call last)
~/miniconda3/envs/napdev/lib/python3.8/site-packages/pydantic/validators.cpython-38-darwin.so in pydantic.validators.find_validators()

TypeError: issubclass() arg 1 must be a class

During handling of the above exception, another exception occurred:

RuntimeError                              Traceback (most recent call last)
<ipython-input-3-3f541325cc4d> in <module>
----> 1 class C(BaseModel):
      2     t: Tuple[Tuple[int], ...] = ()
      3

~/miniconda3/envs/napdev/lib/python3.8/site-packages/pydantic/main.cpython-38-darwin.so in pydantic.main.ModelMetaclass.__new__()

~/miniconda3/envs/napdev/lib/python3.8/site-packages/pydantic/fields.cpython-38-darwin.so in pydantic.fields.ModelField.infer()

~/miniconda3/envs/napdev/lib/python3.8/site-packages/pydantic/fields.cpython-38-darwin.so in pydantic.fields.ModelField.__init__()

~/miniconda3/envs/napdev/lib/python3.8/site-packages/pydantic/fields.cpython-38-darwin.so in pydantic.fields.ModelField.prepare()

~/miniconda3/envs/napdev/lib/python3.8/site-packages/pydantic/fields.cpython-38-darwin.so in pydantic.fields.ModelField.populate_validators()

~/miniconda3/envs/napdev/lib/python3.8/site-packages/pydantic/validators.cpython-38-darwin.so in find_validators()

RuntimeError: error checking inheritance of typing.Tuple[int] (type: Tuple[int])

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.8
            pydantic compiled: True
                 install path: ~/miniconda3/envs/napdev/lib/python3.8/site-packages/pydantic
               python version: 3.8.6 | packaged by conda-forge | (default, Jan 25 2021, 23:22:12)  [Clang 11.0.1 ]
                     platform: macOS-10.15.7-x86_64-i386-64bit
     optional deps. installed: ['typing-extensions']

[PrettyWood]

Hi @tlambert03 and thanks for reporting 🙏
Indeed I changed recently the code related to tuple to be more explicit and support () (empty tuple) but missed the case of Ellipsis with compound type as first argument.
I open a PR to fix this 👍