title: pycryptodome setup.py causing an error when installing pyrebase
body: <p>I am trying to install Pyrebase, but I keep getting an error that I believe is caused by setup.py for pycryptodome. I have searched all over but cannot find a solution, does anyone know how to solve this? </p>
  
  <p>My output is below - I added in (...) in places to truncate the output, which was creating and copying libraries. </p>
  
  <p>Thanks for the help</p>
  
  <pre><code>(backend-ragxWAh7) bash-3.2$ pip install Pyrebase
  Collecting Pyrebase
   (...)
  Building wheels for collected packages: pycryptodome
    Running setup.py bdist_wheel for pycryptodome ... error
    Complete output from command /Users/rafilurie/.local/share/virtualenvs/backend-ragxWAh7/bin/python -u -c "import setuptools, tokenize;__file__='/private/var/folders/d5/zwblxz7d3gxcks_wgjcyxw_00000gn/T/pip-install-q_NyfS/pycryptodome/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" bdist_wheel -d /private/var/folders/d5/zwblxz7d3gxcks_wgjcyxw_00000gn/T/pip-wheel-8ox7HU --python-tag cp27:
    running bdist_wheel
    running build
    running build_py
    creating build
    creating build/lib.macosx-10.14-intel-2.7
    creating build/lib.macosx-10.14-intel-2.7/Crypto
    copying lib/Crypto/__init__.py -&gt; build/lib.macosx-10.14-intel-2.7/Crypto
    (...)
    copying lib/Crypto/SelfTest/Signature/test_vectors/PKCS1-PSS/SigVerPSS_186-3.rsp -&gt; build/lib.macosx-10.14-intel-2.7/Crypto/SelfTest/Signature/test_vectors/PKCS1-PSS
    warning: PCTBuildPy: byte-compiling is disabled, skipping.
  
    running build_ext
    warning: no support for Intel AESNI instructions
    building 'Crypto.Hash._MD2' extension
    creating build/temp.macosx-10.14-intel-2.7
    creating build/temp.macosx-10.14-intel-2.7/src
    cc -fno-strict-aliasing -fno-common -dynamic -g -Os -pipe -fno-common -fno-strict-aliasing -fwrapv -DENABLE_DTRACE -DMACOSX -DNDEBUG -Wall -Wstrict-prototypes -Wshorten-64-to-32 -DNDEBUG -g -fwrapv -Os -Wall -Wstrict-prototypes -DENABLE_DTRACE -arch i386 -arch x86_64 -pipe -DLTC_NO_ASM -Isrc/ -I/System/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c src/MD2.c -o build/temp.macosx-10.14-intel-2.7/src/MD2.o
    xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
    error: command 'cc' failed with exit status 1
  
    ----------------------------------------
    Failed building wheel for pycryptodome
    Running setup.py clean for pycryptodome
  Failed to build pycryptodome
  Installing collected packages: pycryptodome, Pyrebase
    Running setup.py install for pycryptodome ... error
      Complete output from command /Users/rafilurie/.local/share/virtualenvs/backend-ragxWAh7/bin/python -u -c "import setuptools, tokenize;__file__='/private/var/folders/d5/zwblxz7d3gxcks_wgjcyxw_00000gn/T/pip-install-q_NyfS/pycryptodome/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /private/var/folders/d5/zwblxz7d3gxcks_wgjcyxw_00000gn/T/pip-record-1TJZWz/install-record.txt --single-version-externally-managed --compile --install-headers /Users/rafilurie/.local/share/virtualenvs/backend-ragxWAh7/include/site/python2.7/pycryptodome:
      running install
      running build
      running build_py
      (...)
      creating build/lib.macosx-10.14-intel-2.7/Crypto/SelfTest/Signature/test_vectors/PKCS1-v1.5
      copying lib/Crypto/SelfTest/Signature/test_vectors/PKCS1-v1.5/SigVer15_186-3.rsp -&gt; build/lib.macosx-10.14-intel-2.7/Crypto/SelfTest/Signature/test_vectors/PKCS1-v1.5
      copying lib/Crypto/SelfTest/Signature/test_vectors/PKCS1-v1.5/SigGen15_186-3.txt -&gt; build/lib.macosx-10.14-intel-2.7/Crypto/SelfTest/Signature/test_vectors/PKCS1-v1.5
      copying lib/Crypto/SelfTest/Signature/test_vectors/PKCS1-v1.5/SigGen15_186-2.txt -&gt; build/lib.macosx-10.14-intel-2.7/Crypto/SelfTest/Signature/test_vectors/PKCS1-v1.5
      creating build/lib.macosx-10.14-intel-2.7/Crypto/SelfTest/Signature/test_vectors/PKCS1-PSS
      copying lib/Crypto/SelfTest/Signature/test_vectors/PKCS1-PSS/SigGenPSS_186-2.txt -&gt; build/lib.macosx-10.14-intel-2.7/Crypto/SelfTest/Signature/test_vectors/PKCS1-PSS
      copying lib/Crypto/SelfTest/Signature/test_vectors/PKCS1-PSS/SigGenPSS_186-3.txt -&gt; build/lib.macosx-10.14-intel-2.7/Crypto/SelfTest/Signature/test_vectors/PKCS1-PSS
      copying lib/Crypto/SelfTest/Signature/test_vectors/PKCS1-PSS/SigVerPSS_186-3.rsp -&gt; build/lib.macosx-10.14-intel-2.7/Crypto/SelfTest/Signature/test_vectors/PKCS1-PSS
      warning: PCTBuildPy: byte-compiling is disabled, skipping.
  
      running build_ext
      warning: no support for Intel AESNI instructions
      building 'Crypto.Hash._MD2' extension
      creating build/temp.macosx-10.14-intel-2.7
      creating build/temp.macosx-10.14-intel-2.7/src
      cc -fno-strict-aliasing -fno-common -dynamic -g -Os -pipe -fno-common -fno-strict-aliasing -fwrapv -DENABLE_DTRACE -DMACOSX -DNDEBUG -Wall -Wstrict-prototypes -Wshorten-64-to-32 -DNDEBUG -g -fwrapv -Os -Wall -Wstrict-prototypes -DENABLE_DTRACE -arch i386 -arch x86_64 -pipe -DLTC_NO_ASM -Isrc/ -I/System/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c src/MD2.c -o build/temp.macosx-10.14-intel-2.7/src/MD2.o
      xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
      error: command 'cc' failed with exit status 1
  
      ----------------------------------------
  Command "/Users/rafilurie/.local/share/virtualenvs/backend-ragxWAh7/bin/python -u -c "import setuptools, tokenize;__file__='/private/var/folders/d5/zwblxz7d3gxcks_wgjcyxw_00000gn/T/pip-install-q_NyfS/pycryptodome/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /private/var/folders/d5/zwblxz7d3gxcks_wgjcyxw_00000gn/T/pip-record-1TJZWz/install-record.txt --single-version-externally-managed --compile --install-headers /Users/rafilurie/.local/share/virtualenvs/backend-ragxWAh7/include/site/python2.7/pycryptodome" failed with error code 1 in /private/var/folders/d5/zwblxz7d3gxcks_wgjcyxw_00000gn/T/pip-install-q_NyfS/pycryptodome/
  </code></pre>