BLD: Remove hard installation dep

.flake8

@@ -17,5 +17,8 @@ ignore =
     # Useful to ignore for "import keras.backend as K"
     N812
 
-#imported but unused in __init__.py, that's ok.
-per-file-ignores = **/__init__.py:F401
+per-file-ignores =
+    # imported but unused in __init__.py, that's ok.
+    **/__init__.py:F401
+    # import not at top okay due to TF installation check
+    tensorflow_addons/__init__.py:F401,E402

build_deps/build-requirements.txt

@@ -0,0 +1 @@
+tensorflow==2.1.0

build_deps/build_pip_pkg.sh

@@ -44,6 +44,13 @@ function main() {
     exit 1
   fi
 
+  # Check if python3 is available. On Windows VM it is not.
+  if [ -x "$(command -v python3)" ]; then
+      _PYTHON_BINARY=python3
+    else
+      _PYTHON_BINARY=python
+  fi
+
   mkdir -p ${DEST}
   DEST=$(abspath "${DEST}")
   echo "=== destination directory: ${DEST}"
@@ -72,9 +79,9 @@ function main() {
 
   if [[ -z ${BUILD_FLAG} ]]; then
     # Windows has issues with locking library files for deletion so do not fail here
-    ${PYTHON_VERSION:=python} setup.py bdist_wheel || true
+    ${_PYTHON_BINARY} setup.py bdist_wheel || true
   else
-    ${PYTHON_VERSION:=python} setup.py bdist_wheel "${2}" || true
+    ${_PYTHON_BINARY} setup.py bdist_wheel "${2}" || true
   fi
 
   cp dist/*.whl "${DEST}"

build_deps/check_deps.py

@@ -26,8 +26,9 @@ def check_dependencies(requirement_file_name):
     except DistributionNotFound as e:
         print(e)
         sys.exit(1)
-    sys.exit(0)
 
 
 if __name__ == "__main__":
     check_dependencies("requirements.txt")
+    check_dependencies("build_deps/build-requirements.txt")
+    sys.exit(0)

configure.py

@@ -102,6 +102,9 @@ def generate_shared_lib_name(namespec):
 with open("requirements.txt") as f:
     _REQUIRED_PKG = f.read().splitlines()
 
+with open("build_deps/build-requirements.txt") as f:
+    _REQUIRED_PKG.extend(f.read().splitlines())
+
 print()
 print("> TensorFlow Addons will link to the framework in a pre-installed TF pacakge...")
 print("> Checking installed packages in {}".format(_PYTHON_PATH))
@@ -116,7 +119,7 @@ def generate_shared_lib_name(namespec):
         print("> Installing...")
         install_cmd = [_PYTHON_PATH, "-m", "pip", "install"]
         install_cmd.extend(_PIP_INSTALL_OPTS)
-        install_cmd.extend(["-r", "requirements.txt"])
+        install_cmd.extend(_REQUIRED_PKG)
         subprocess.check_call(install_cmd)
     else:
         print("> Exiting...")

requirements.txt

@@ -1,2 +1 @@
-tensorflow==2.1.0
 typeguard

tensorflow_addons/__init__.py

@@ -13,6 +13,9 @@
 # limitations under the License.
 # ==============================================================================
 """Useful extra functionality for TensorFlow maintained by SIG-addons."""
+from tensorflow_addons.utils.ensure_tf_install import _ensure_tf_install
+
+_ensure_tf_install()
 
 # Local project imports
 from tensorflow_addons import activations

tensorflow_addons/utils/ensure_tf_install.py

@@ -0,0 +1,43 @@
+# Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+
+
+# Ensure TensorFlow is importable and its version is sufficiently recent. This
+# needs to happen before anything else, since the imports below will try to
+# import tensorflow, too.
+def _ensure_tf_install():
+    """Attempt to import tensorflow, and ensure its version is sufficient.
+    Raises:
+      ImportError: if either tensorflow is not importable or its version is
+      inadequate.
+    """
+    import tensorflow as tf
+    import distutils.version
+
+    #
+    # Update this whenever we need to depend on a newer TensorFlow release.
+    #
+    required_tensorflow_version = "2.1.0"
+
+    if distutils.version.LooseVersion(tf.__version__) < distutils.version.LooseVersion(
+        required_tensorflow_version
+    ):
+        raise ImportError(
+            "This version of TensorFlow Addons requires TensorFlow "
+            "version >= {required}; Detected an installation of version "
+            "{present}. Please upgrade TensorFlow to proceed.".format(
+                required=required_tensorflow_version, present=tf.__version__
+            )
+        )

tools/ci_testing/addons_cpu.sh

@@ -40,6 +40,7 @@ echo ""
 export CC_OPT_FLAGS='-mavx'
 export TF_NEED_CUDA=0
 
+# Check if python3 is available. On Windows VM it is not.
 if [ -x "$(command -v python3)" ]; then
     echo 'y' | python3 ./configure.py
   else

tools/ci_testing/addons_gpu.sh

@@ -43,7 +43,7 @@ export CUDA_TOOLKIT_PATH="/usr/local/cuda"
 export TF_CUDNN_VERSION="7"
 export CUDNN_INSTALL_PATH="/usr/lib/x86_64-linux-gnu"
 
-# Check if python3 is available. On Windows it is not.
+# Check if python3 is available. On Windows VM it is not.
 if [ -x "$(command -v python3)" ]; then
     echo 'y' | python3 ./configure.py
   else