MAINT: Avoid SyntaxWarnings on import in Python 3.8

Various Python 3.9 related import changes

fractions.gcd() function has been removed from Python 3.9, it was
deprecated since Python 3.5.

https://docs.python.org/3.9/whatsnew/3.9.html#removed

See https://github.com/Theano/Theano/pull/6664#issuecomment-581845517

Counteract hypot redefinition for old Python versions

fix doc warning

Fix simple typo: varible->size -> variable->size

Closes #6734

Fix subtensor numpy warning

use string_types instead of str in get_substream_rstates dtype assertion

Using Theano 1.0.4 via Keras 2.2.5 under Python 2.7.12, calling `keras.model.model_from_json()` for model deserialization fails at this assertion in theano at `get_substream_rstates` because `json.loads()` as called by Keras is returning a dict with unicode objects as values. This PR fixes the problem.

Fix deprecation warning.

Change the import of `Iterable` from `collections.Iterable` to `collections.abc.Iterable` to future-proof against Python 3.7.8.

Ignore new error that we didn't enforced before.

Fix pygment version. Its packages pkgs/main/noarch::pygments-2.4.2-py_0 get installed in Python 3.4, but it give an error that is doesnt support it.

Casting `diagonal_slice` to tuple eliminates a FutureWarning from numpy that could cause an error down the line.

added test for output shape of frac bilinear upsampling

Update the documentation on gpuarray.sched

Update the documentation on how to upload the package to PyPI

Fixed shape error of frac bilinear upsample

fixed bilinear_kernel_1D to return a float32 tensor