clarify error message when apt-get source=ver fails, print a real error message instead of "ignoring"

cmdline/apt-get.cc

@@ -416,7 +416,7 @@ pkgSrcRecords::Parser *FindSrc(const char *Name,pkgRecords &Recs,
 
       if (Last != 0 || VerTag.empty() == true)
 	 break;
-      _error->Error(_("Ignore unavailable version '%s' of package '%s'"), VerTag.c_str(), TmpSrc.c_str());
+      _error->Error(_("Can not find version '%s' of package '%s'"), VerTag.c_str(), TmpSrc.c_str());
       return 0;
    }
 

test/integration/test-apt-get-source

@@ -62,7 +62,7 @@ Need to get 0 B of source archives.
 
 # unavailable one
 testequal "$HEADER
-E: Ignore unavailable version '9.9-not-there' of package 'foo'
+E: Can not find version '9.9-not-there' of package 'foo'
 E: Unable to find a source package for foo" aptget source -q --print-uris foo=9.9-not-there
 
 # version and release