work on xapian-delve issues

1) `xapian_wheel_builder.sh` adds `xapian-delve` to the wheel
2) `tests/xapian_tests/tests/test_backend.py` learns to check the new `xapian-delve` location
3) drop support for delve from xapian<1.3 (support dropped along Python 2)

tests/xapian_tests/tests/test_backend.py

@@ -1,5 +1,6 @@
 from decimal import Decimal
 import datetime
+import inspect
 import sys
 import xapian
 import subprocess
@@ -30,17 +31,17 @@ class XapianSearchResult(SearchResult):
 
 
 def get_terms(backend, *args):
-    if XAPIAN_VERSION[1] <= 2:
-        # old versions use "delve".
-        executable = 'delve'
-    else:
-        # new versions use 'xapian-delve'
-        executable = 'xapian-delve'
+    executable = 'xapian-delve'
 
     # dev versions (odd minor) use a suffix
     if XAPIAN_VERSION[1] % 2 != 0:
         executable = executable+'-%d.%d' % tuple(XAPIAN_VERSION[0:2])
 
+    # look for a xapian-delve built by `xapian_wheel_builder`
+    wheel_delve = os.path.join(os.path.dirname(inspect.getfile(xapian)), executable)
+    if os.path.exists(wheel_delve):
+        executable = wheel_delve
+
     result = subprocess.check_output([executable] + list(args) + [backend.path],
                                      env=os.environ.copy()).decode('utf-8')
     result = result.split(": ")

xapian_wheel_builder.sh

@@ -135,8 +135,8 @@ echo "Building xapian python3 bindings..."
     make install
 )
 
-echo "preparing xapian wheel..."
-for file in "${prefix}"/xapian/*.so; do
+binary_patch_rpath() {
+    file="${1}"
     case "${uname_sysname}" in
         Linux|FreeBSD)
             # Binary patch rpath to be '$ORIGIN' as needed.
@@ -151,6 +151,11 @@ for file in "${prefix}"/xapian/*.so; do
             install_name_tool -change "${prefix}/lib/${libxapian_name}" "@loader_path/${libxapian_name}" "${file}"
             ;;
     esac
+}
+
+echo "preparing xapian wheel..."
+for file in "${prefix}"/xapian/*.so; do
+    binary_patch_rpath "${file}"
 done
 
 # Copy libxapian into place alongside the python bindings.
@@ -161,6 +166,11 @@ case "${uname_sysname}" in
         ;;
 esac
 
+for file in "${prefix}"/bin/xapian-delve*; do
+    binary_patch_rpath "${file}"
+    cp "${file}" "${prefix}/xapian"
+done
+
 # Prepare the scaffolding for the wheel
 cat > "$prefix/setup.py" <<EOF
 from setuptools import setup