reorganize travis configuration, remove runtests.py

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Linux builds:

• conda builds
• based on pip and Ubuntu 18.04 packages
• Python versions 2.7 to 3.8

OSX builds:

• CONDA with custom SDK (curretly not functional, see discussion on Travis OSX builds are failing #76 and PR Fix osx build #92)
• native osx / pip packages

Replaced old runtests.py with direct pytest call

(conflicts with #92)

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Note that the MacOS X build using miniconda still fails because it cannot link the correct libraries

- Check for working C compiler: $BUILD_PREFIX/bin/x86_64-apple-darwin13.4.0-clang -- broken
848CMake Error at /Users/travis/miniconda/conda-bld/slycot_1580800368543/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pla/share/cmake-3.14/Modules/CMakeTestCCompiler.cmake:60 (message):
849  The C compiler
850
851    "/Users/travis/miniconda/conda-bld/slycot_1580800368543/_build_env/bin/x86_64-apple-darwin13.4.0-clang"
852
853  is not able to compile a simple test program.
854
855  It fails with the following output:
856
857    Change Dir: /Users/travis/miniconda/conda-bld/slycot_1580800368543/work/_cmake_test_compile/build/CMakeFiles/CMakeTmp
858    
859    Run Build Command(s):/usr/bin/make cmTC_be759/fast 
860    /Applications/Xcode-9.4.1.app/Contents/Developer/usr/bin/make -f CMakeFiles/cmTC_be759.dir/build.make CMakeFiles/cmTC_be759.dir/build
861    Building C object CMakeFiles/cmTC_be759.dir/testCCompiler.c.o
862    /Users/travis/miniconda/conda-bld/slycot_1580800368543/_build_env/bin/x86_64-apple-darwin13.4.0-clang   -march=core2 -mtune=haswell -mssse3 -ftree-vectorize -fPIC -fPIE -fstack-protector-strong -O2 -pipe -I/Users/travis/miniconda/conda-bld/slycot_1580800368543/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pla/include -fdebug-prefix-map=/Users/travis/miniconda/conda-bld/slycot_1580800368543/work=/usr/local/src/conda/slycot-0.3.5 -fdebug-prefix-map=/Users/travis/miniconda/conda-bld/slycot_1580800368543/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pla=/usr/local/src/conda-prefix -isysroot /opt/MacOSX10.9.sdk  -arch x86_64 -isysroot /opt/MacOSX10.9.sdk -mmacosx-version-min=10.9   -o CMakeFiles/cmTC_be759.dir/testCCompiler.c.o   -c /Users/travis/miniconda/conda-bld/slycot_1580800368543/work/_cmake_test_compile/build/CMakeFiles/CMakeTmp/testCCompiler.c
863    Linking C executable cmTC_be759
864    /Users/travis/miniconda/conda-bld/slycot_1580800368543/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pla/bin/cmake -E cmake_link_script CMakeFiles/cmTC_be759.dir/link.txt --verbose=1
865    /Users/travis/miniconda/conda-bld/slycot_1580800368543/_build_env/bin/x86_64-apple-darwin13.4.0-clang -march=core2 -mtune=haswell -mssse3 -ftree-vectorize -fPIC -fPIE -fstack-protector-strong -O2 -pipe -I/Users/travis/miniconda/conda-bld/slycot_1580800368543/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pla/include -fdebug-prefix-map=/Users/travis/miniconda/conda-bld/slycot_1580800368543/work=/usr/local/src/conda/slycot-0.3.5 -fdebug-prefix-map=/Users/travis/miniconda/conda-bld/slycot_1580800368543/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pla=/usr/local/src/conda-prefix -isysroot /opt/MacOSX10.9.sdk  -arch x86_64 -isysroot /opt/MacOSX10.9.sdk -mmacosx-version-min=10.9 -Wl,-search_paths_first -Wl,-headerpad_max_install_names -Wl,-pie -Wl,-headerpad_max_install_names -Wl,-dead_strip_dylibs -Wl,-rpath,/Users/travis/miniconda/conda-bld/slycot_1580800368543/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pla/lib -L/Users/travis/miniconda/conda-bld/slycot_1580800368543/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pla/lib -v -isysroot /opt/MacOSX10.9.sdk  CMakeFiles/cmTC_be759.dir/testCCompiler.c.o  -o cmTC_be759 
866    clang version 4.0.1 (tags/RELEASE_401/final)
867    Target: x86_64-apple-darwin13.4.0
868    Thread model: posix
869    InstalledDir: /Users/travis/miniconda/conda-bld/slycot_1580800368543/_build_env/bin
870     "/Users/travis/miniconda/conda-bld/slycot_1580800368543/_build_env/bin/x86_64-apple-darwin13.4.0-ld" -demangle -lto_library /Users/travis/miniconda/conda-bld/slycot_1580800368543/_build_env/lib/libLTO.dylib -dynamic -arch x86_64 -macosx_version_min 10.9.0 -pie -syslibroot /opt/MacOSX10.9.sdk -o cmTC_be759 -L/Users/travis/miniconda/conda-bld/slycot_1580800368543/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pla/lib -search_paths_first -headerpad_max_install_names -pie -headerpad_max_install_names -dead_strip_dylibs -rpath /Users/travis/miniconda/conda-bld/slycot_1580800368543/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pla/lib CMakeFiles/cmTC_be759.dir/testCCompiler.c.o -lSystem /Users/travis/miniconda/conda-bld/slycot_1580800368543/_build_env/bin/../lib/clang/4.0.1/lib/darwin/libclang_rt.osx.a
871    ld: library not found for -lSystem

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@repagh, I found the issue: The unpacking the tarball already creates the subdir. This works:

Slycot/.travis.yml

Lines 92 to 93 in 4ea90b0

	wget https://github.com/phracker/MacOSX-SDKs/releases/download/10.15/MacOSX10.9.sdk.tar.xz
	sudo tar -C /opt -xJf MacOSX10.9.sdk.tar.xz

[bnavigator]

... great. Now Travis fails because it could not clone python-control due to a transient connection issue on the second job.