This patch allows us to build libextractor against exiv2 0.27.x.
Adapted from this upstream commit:

  commit 1ecee9a47717e36cb8a3925d011d1a6de11d631c
  Author: Christian Grothoff <christian@grothoff.org>
  Date:   Mon Jul 29 17:58:18 2019 +0200

      importing patch from Gentoo/AS to address exiv2 build issue (#5820)

diff --git a/src/plugins/exiv2_extractor.cc b/src/plugins/exiv2_extractor.cc
index 8741d40..ef402a8 100644
--- a/src/plugins/exiv2_extractor.cc
+++ b/src/plugins/exiv2_extractor.cc
@@ -27,10 +27,7 @@
 #include <cassert>
 #include <cstring>
 #include <math.h>
-#include <exiv2/exif.hpp>
-#include <exiv2/error.hpp>
-#include <exiv2/image.hpp>
-#include <exiv2/futils.hpp>
+#include <exiv2/exiv2.hpp>
 
 /**
  * Enable debugging to get error messages.
@@ -180,7 +177,7 @@ public:
    *
    * @return -1 on error
    */
-#if EXIV2_VERSION >= EXIV2_MAKE_VERSION(0,26,0)
+#if EXIV2_TEST_VERSION(0,26,0)
   virtual size_t size (void) const;
 #else
   virtual long int size (void) const;
@@ -316,7 +313,11 @@ ExtractorIO::getb ()
   const unsigned char *r;
 
   if (1 != ec->read (ec->cls, &data, 1))
+#if EXIV2_TEST_VERSION(0,27,0)
+    throw Exiv2::BasicError<char> (Exiv2::kerDecodeLangAltQualifierFailed);
+#else
     throw Exiv2::BasicError<char> (42 /* error code */);
+#endif
   r = (const unsigned char *) data;
   return *r;
 }
@@ -371,7 +372,11 @@ ExtractorIO::putb (Exiv2::byte data)
 void
 ExtractorIO::transfer (Exiv2::BasicIo& src)
 {
+#if EXIV2_TEST_VERSION(0,27,0)
+    throw Exiv2::BasicError<char> (Exiv2::kerDecodeLangAltQualifierFailed);
+#else
   throw Exiv2::BasicError<char> (42 /* error code */);
+#endif
 }
 
 
@@ -416,7 +421,11 @@ ExtractorIO::seek (long offset,
 Exiv2::byte *
 ExtractorIO::mmap (bool isWritable)
 {
+#if EXIV2_TEST_VERSION(0,27,0)
+    throw Exiv2::BasicError<char> (Exiv2::kerDecodeLangAltQualifierFailed);
+#else
   throw Exiv2::BasicError<char> (42 /* error code */);
+#endif
 }
 
 
@@ -449,7 +458,7 @@ ExtractorIO::tell (void) const
  *
  * @return -1 on error
  */
-#if EXIV2_VERSION >= EXIV2_MAKE_VERSION(0,26,0)
+#if EXIV2_TEST_VERSION(0,26,0)
 size_t
 #else
 long int
@@ -504,7 +513,11 @@ ExtractorIO::eof () const
 std::string
 ExtractorIO::path () const
 {
+#if EXIV2_TEST_VERSION(0,27,0)
+    throw Exiv2::BasicError<char> (Exiv2::kerDecodeLangAltQualifierFailed);
+#else
   throw Exiv2::BasicError<char> (42 /* error code */);
+#endif
 }
 
 
@@ -517,7 +530,11 @@ ExtractorIO::path () const
 std::wstring
 ExtractorIO::wpath () const
 {
+#if EXIV2_TEST_VERSION(0,27,0)
+    throw Exiv2::BasicError<char> (Exiv2::kerDecodeLangAltQualifierFailed);
+#else
   throw Exiv2::BasicError<char> (42 /* error code */);
+#endif
 }
 #endif
 
@@ -531,7 +548,11 @@ Exiv2::BasicIo::AutoPtr
 ExtractorIO::temporary () const
 {
   fprintf (stderr, "throwing temporary error\n");
+#if EXIV2_TEST_VERSION(0,27,0)
+    throw Exiv2::BasicError<char> (Exiv2::kerDecodeLangAltQualifierFailed);
+#else
   throw Exiv2::BasicError<char> (42 /* error code */);
+#endif
 }
 
 
@@ -697,7 +718,7 @@ EXTRACTOR_exiv2_extract_method (struct EXTRACTOR_ExtractContext *ec)
 {
   try
     {
-#if EXIV2_MAKE_VERSION(0,23,0) <= EXIV2_VERSION
+#if !EXIV2_TEST_VERSION(0,24,0)
       Exiv2::LogMsg::setLevel (Exiv2::LogMsg::mute);
 #endif
       std::auto_ptr<Exiv2::BasicIo> eio(new ExtractorIO (ec));
