Python 3.7 support

[yongtang]

Python 3.7 is a supported version in TF 1.13.0 (rc2), so we should support 3.7 as well (already saw lots of interests in TF about 3.7).

[yongtang]

Tried to repackage binary with python 3.7 (on Ubuntu 14.04). When running on Ubuntu 18.04 could see the following error:

/usr/local/lib/python3.7/dist-packages/tensorflow_io/image/python/ops/_image_ops.so: undefined symbol: _ZN10tensorflow7strings6StrCatERKNS0_8AlphaNumES3_

A likely cause I guess is that Python 3.7 version of tensorflow is compiled with some flags in gcc (or a different version of gcc).

[wookayin]

I ran into this issue. In my environments was:

• python 3.6 (anaconda)
• Ubuntu 16.04
• g++

where I manually built TF 1.13.0-rc2 from source.

When I was using TF 1.13.0-rc2 from pypi, the error did not happen. In both cases I built tensorflow-io from source (0.4.0, the latest snapshot as of 2/25)

(I suggest to change the title of this issue as Undefined symbol: _ZN10tensorflow7strings6StrCatERKNS0_8AlphaNumE or something like that)

[yongtang]

I haven't tried myself but I guess it may have something to do with the api compatibility. Maybe you could give -copt="-D_GLIBCXX_USE_CXX11_ABI=0" a try when building with bazel for both tensorflow and tensorflow-io?

[yongtang]

Python 3.7 has been added in PR #193 and tensorflow-io-nightly. it will show up in the next version of release (v0.6.0).