Merge pull request tensorflow#37919 from reedwm/none_grad_fix

2.2-rc2 cherry-pick request: Fix crash in Model.fit() if a gradient is None

Merge pull request tensorflow#37704 from geetachavan1/cherrypicks_RB9MM

[r2.2:Cherrypick] Remove the trailing 'm' , since the tag for py38 is not cp38m but cp38.

Merge pull request tensorflow#37486 from tensorflow/mm-r2.2-debug-win…

…-build

Debug windows builds, add `-s` bazel flag

Merge pull request tensorflow#36215 from tensorflow-jenkins/version-n…

…umbers-1.15.2-8214

Update version numbers for TensorFlow 1.15.2

Merge pull request tensorflow#35913 from tensorflow-jenkins/relnotes-…

…2.0.1-6767

Update release notes for TensorFlow 2.0.1

Merge pull request tensorflow#35620 from tensorflow-jenkins/version-n…

…umbers-2.1.0-23859

Update version numbers for TensorFlow 2.1.0

Merge pull request tensorflow#35238 from ROCmSoftwarePlatform/r2.1-ei…

…gen-patch

[ROCm][r2.1] eigen patch needed for HIP header changes

Merge pull request tensorflow#35005 from geetachavan1/cherrypicks_3SVHU

[r2.1:Cherrypick] Expose ndtri and erfinv under tf.math.ndtri and tf.math.erfinv.

Merge pull request tensorflow#34626 from yifeif/cherrypicks_J8PS0

Move gpu script update to the correct file.

Merge pull request tensorflow#31861 from tensorflow-jenkins/relnotes-…

…1.15.0rc0-16184

Update release notes for TensorFlow 1.15.0