[pygobject] setup.py: Also set setup_requires to require pycairo

[Christoph Reiter <creiter src gnome org>]

commit bab1cb0d98e4a6219332394161dbf07aafa0c615
Author: Christoph Reiter <creiter src gnome org>
Date:   Mon Dec 11 16:26:54 2017 +0100

    setup.py: Also set setup_requires to require pycairo
    
    We need pycairo at build time. There are some problems with setup_requires
    in that it isn't directly handled by pip, but let's give it a try and see
    which problems come up.
    
    Thanks to mgedmin for pointing that out

 setup.py |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/setup.py b/setup.py
index 95669db..dbeed65 100644
--- a/setup.py
+++ b/setup.py
@@ -380,6 +380,10 @@ def main():
             "pycairo>=%s" % get_version_requirement(
                 script_dir, get_pycairo_pkg_config_name()),
         ],
+        setup_requires=[
+            "pycairo>=%s" % get_version_requirement(
+                script_dir, get_pycairo_pkg_config_name()),
+        ],
     )