reloc/python3: add install.sh on python relocatable package

To support nonroot installation on scylla-python3, add install.sh on
scylla-python3 relocatable package.

python3/install.sh

@@ -0,0 +1,82 @@
+#!/bin/bash
+#
+# Copyright (C) 2019 ScyllaDB
+#
+
+#
+# This file is part of Scylla.
+#
+# Scylla is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Scylla is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Scylla.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+set -e
+
+print_usage() {
+    cat <<EOF
+Usage: install.sh [options]
+
+Options:
+  --root /path/to/root     alternative install root (default /)
+  --prefix /prefix         directory prefix (default /usr)
+  --nonroot                shortcut of '--disttype nonroot'
+  --help                   this helpful message
+EOF
+    exit 1
+}
+
+root=/
+nonroot=false
+
+while [ $# -gt 0 ]; do
+    case "$1" in
+        "--root")
+            root="$2"
+            shift 2
+            ;;
+        "--prefix")
+            prefix="$2"
+            shift 2
+            ;;
+        "--nonroot")
+            nonroot=true
+            shift 1
+            ;;
+        "--help")
+            shift 1
+	    print_usage
+            ;;
+        *)
+            print_usage
+            ;;
+    esac
+done
+
+if [ -z "$prefix" ]; then
+    if $nonroot; then
+        prefix=~/scylladb
+    else
+        prefix=/opt/scylladb
+    fi
+fi
+
+rprefix=$(realpath -m "$root/$prefix")
+
+install -d -m755 "$rprefix"/python3/bin
+cp -r ./bin/* "$rprefix"/python3/bin
+install -d -m755 "$rprefix"/python3/lib64
+cp -r ./lib64/* "$rprefix"/python3/lib64
+install -d -m755 "$rprefix"/python3/libexec
+cp -r ./libexec/* "$rprefix"/python3/libexec
+install -d -m755 "$rprefix"/python3/licenses
+cp -r ./licenses/* "$rprefix"/python3/licenses