title: Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed in Python3?
body: <p>I am hitting this error when tried to run <code>pip install lxm</code> in <strong>Windows 10</strong>. Any prerequisites for <code>lxml</code>?</p>
  
  <pre><code>C:\Python37-32\Scripts&gt;pip install lxml
  Collecting lxml
    Using cached https://files.pythonhosted.org/packages/54/a6/43be8cf1cc23e3fa208cab04ba2f9c3b7af0233aab32af6b5089122b44cd/lxml-4.2.3.tar.gz
  Installing collected packages: lxml
    Running setup.py install for lxml ... error
      Complete output from command c:\python37-32\python.exe -u -c "import setuptools, tokenize;__file__='C:\\Users\\hp\\AppData\\Local\\Temp\\pip-install-12zn4_mn\\lxml\\setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record C:\Users\hp\AppData\Local\Temp\pip-record-ag0n7oku\install-record.txt --single-version-externally-managed --compile:
      Building lxml version 4.2.3.
      Building without Cython.
      ERROR: b"'xslt-config' is not recognized as an internal or external command,\r\noperable program or batch file.\r\n"
      ** make sure the development packages of libxml2 and libxslt are installed **
  
      Using build configuration of libxslt
      running install
      running build
      running build_py
      creating build
      creating build\lib.win-amd64-3.7
      creating build\lib.win-amd64-3.7\lxml
      copying src\lxml\builder.py -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\cssselect.py -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\doctestcompare.py -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\ElementInclude.py -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\pyclasslookup.py -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\sax.py -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\usedoctest.py -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\_elementpath.py -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\__init__.py -&gt; build\lib.win-amd64-3.7\lxml
      creating build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\__init__.py -&gt; build\lib.win-amd64-3.7\lxml\includes
      creating build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\builder.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\clean.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\defs.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\diff.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\ElementSoup.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\formfill.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\html5parser.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\soupparser.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\usedoctest.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\_diffcommand.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\_html5builder.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\_setmixin.py -&gt; build\lib.win-amd64-3.7\lxml\html
      copying src\lxml\html\__init__.py -&gt; build\lib.win-amd64-3.7\lxml\html
      creating build\lib.win-amd64-3.7\lxml\isoschematron
      copying src\lxml\isoschematron\__init__.py -&gt; build\lib.win-amd64-3.7\lxml\isoschematron
      copying src\lxml\etree.h -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\etree_api.h -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\lxml.etree.h -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\lxml.etree_api.h -&gt; build\lib.win-amd64-3.7\lxml
      copying src\lxml\includes\c14n.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\config.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\dtdvalid.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\etreepublic.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\htmlparser.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\relaxng.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\schematron.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\tree.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\uri.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\xinclude.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\xmlerror.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\xmlparser.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\xmlschema.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\xpath.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\xslt.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\__init__.pxd -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\etree_defs.h -&gt; build\lib.win-amd64-3.7\lxml\includes
      copying src\lxml\includes\lxml-version.h -&gt; build\lib.win-amd64-3.7\lxml\includes
      creating build\lib.win-amd64-3.7\lxml\isoschematron\resources
      creating build\lib.win-amd64-3.7\lxml\isoschematron\resources\rng
      copying src\lxml\isoschematron\resources\rng\iso-schematron.rng -&gt; build\lib.win-amd64-3.7\lxml\isoschematron\resources\rng
      creating build\lib.win-amd64-3.7\lxml\isoschematron\resources\xsl
      copying src\lxml\isoschematron\resources\xsl\RNG2Schtrn.xsl -&gt; build\lib.win-amd64-3.7\lxml\isoschematron\resources\xsl
      copying src\lxml\isoschematron\resources\xsl\XSD2Schtrn.xsl -&gt; build\lib.win-amd64-3.7\lxml\isoschematron\resources\xsl
      creating build\lib.win-amd64-3.7\lxml\isoschematron\resources\xsl\iso-schematron-xslt1
      copying src\lxml\isoschematron\resources\xsl\iso-schematron-xslt1\iso_abstract_expand.xsl -&gt; build\lib.win-amd64-3.7\lxml\isoschematron\resources\xsl\iso-schematron-xslt1
      copying src\lxml\isoschematron\resources\xsl\iso-schematron-xslt1\iso_dsdl_include.xsl -&gt; build\lib.win-amd64-3.7\lxml\isoschematron\resources\xsl\iso-schematron-xslt1
      copying src\lxml\isoschematron\resources\xsl\iso-schematron-xslt1\iso_schematron_message.xsl -&gt; build\lib.win-amd64-3.7\lxml\isoschematron\resources\xsl\iso-schematron-xslt1
      copying src\lxml\isoschematron\resources\xsl\iso-schematron-xslt1\iso_schematron_skeleton_for_xslt1.xsl -&gt; build\lib.win-amd64-3.7\lxml\isoschematron\resources\xsl\iso-schematron-xslt1
      copying src\lxml\isoschematron\resources\xsl\iso-schematron-xslt1\iso_svrl_for_xslt1.xsl -&gt; build\lib.win-amd64-3.7\lxml\isoschematron\resources\xsl\iso-schematron-xslt1
      copying src\lxml\isoschematron\resources\xsl\iso-schematron-xslt1\readme.txt -&gt; build\lib.win-amd64-3.7\lxml\isoschematron\resources\xsl\iso-schematron-xslt1
      running build_ext
      building 'lxml.etree' extension
      creating build\temp.win-amd64-3.7
      creating build\temp.win-amd64-3.7\Release
      creating build\temp.win-amd64-3.7\Release\src
      creating build\temp.win-amd64-3.7\Release\src\lxml
      C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.14.26428\bin\HostX86\x64\cl.exe /c /nologo /Ox /W3 /GL /DNDEBUG /MD -DCYTHON_CLINE_IN_TRACEBACK=0 -Isrc -Isrc\lxml\includes -Ic:\python37-32\include -Ic:\python37-32\include "-IC:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.14.26428\ATLMFC\include" "-IC:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.14.26428\include" "-IC:\Program Files (x86)\Windows Kits\NETFXSDK\4.6.1\include\um" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.17134.0\ucrt" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.17134.0\shared" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.17134.0\um" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.17134.0\winrt" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.17134.0\cppwinrt" /Tcsrc\lxml\etree.c /Fobuild\temp.win-amd64-3.7\Release\src\lxml\etree.obj -w
      cl : Command line warning D9025 : overriding '/W3' with '/w'
      etree.c
      c:\users\hp\appdata\local\temp\pip-install-12zn4_mn\lxml\src\lxml\includes/etree_defs.h(14): fatal error C1083: Cannot open include file: 'libxml/xmlversion.h': No such file or directory
      Compile failed: command 'C:\\Program Files (x86)\\Microsoft Visual Studio\\2017\\Community\\VC\\Tools\\MSVC\\14.14.26428\\bin\\HostX86\\x64\\cl.exe' failed with exit status 2
      creating Users
      creating Users\hp
      creating Users\hp\AppData
      creating Users\hp\AppData\Local
      creating Users\hp\AppData\Local\Temp
      C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.14.26428\bin\HostX86\x64\cl.exe /c /nologo /Ox /W3 /GL /DNDEBUG /MD -I/usr/include/libxml2 "-IC:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.14.26428\ATLMFC\include" "-IC:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.14.26428\include" "-IC:\Program Files (x86)\Windows Kits\NETFXSDK\4.6.1\include\um" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.17134.0\ucrt" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.17134.0\shared" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.17134.0\um" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.17134.0\winrt" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.17134.0\cppwinrt" /TcC:\Users\hp\AppData\Local\Temp\xmlXPathInitws24hybn.c /FoUsers\hp\AppData\Local\Temp\xmlXPathInitws24hybn.obj
      xmlXPathInitws24hybn.c
      C:\Users\hp\AppData\Local\Temp\xmlXPathInitws24hybn.c(1): fatal error C1083: Cannot open include file: 'libxml/xpath.h': No such file or directory
      error: command 'C:\\Program Files (x86)\\Microsoft Visual Studio\\2017\\Community\\VC\\Tools\\MSVC\\14.14.26428\\bin\\HostX86\\x64\\cl.exe' failed with exit status 2
      *********************************************************************************
      Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed?
      *********************************************************************************
  
      ----------------------------------------
  Command "c:\python37-32\python.exe -u -c "import setuptools, tokenize;__file__='C:\\Users\\hp\\AppData\\Local\\Temp\\pip-install-12zn4_mn\\lxml\\setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record C:\Users\hp\AppData\Local\Temp\pip-record-ag0n7oku\install-record.txt --single-version-externally-managed --compile" failed with error code 1 in C:\Users\hp\AppData\Local\Temp\pip-install-12zn4_mn\lxml\
  </code></pre>