djtest: use pyelftools to find uwsgi ld.so

Change-Id: I54bdaa588ff15d8c6ca73c4307076a93a5682d78

personal/q3k/djtest/BUILD

@@ -5,6 +5,7 @@ py_library(
     srcs = glob(["djtest/**/*.py"]),
     deps = [
         requirement("django"),
+        requirement("pytz"),
         requirement("sqlparse"),
     ],
 )
@@ -24,5 +25,6 @@ py_binary(
        ":app",
        "@bazel_tools//tools/python/runfiles",
         requirement("uwsgi"),
+        requirement("pyelftools"),
     ],
 )

personal/q3k/djtest/uwsgi-start.py

@@ -6,13 +6,24 @@ import tempfile
 import bazel_tools
 import bazel_tools.tools.python
 
+from elftools.elf.elffile import ELFFile
+from elftools.elf.segments import InterpSegment
+
 from bazel_tools.tools.python.runfiles import runfiles
 r = runfiles.Create()
 
 uwsgi = r.Rlocation("pydeps_pypi__uWSGI_2_0_18/uWSGI-2.0.18.data/scripts/uwsgi")
-print(uwsgi)
 settings = r.Rlocation("hscloud/personal/q3k/djtest/djtest/settings.py")
-print(settings)
+
+# uwsgi from runfiles is non-chmodded, we have to run it through its interpreter
+ld = None
+with open(uwsgi, 'rb') as f:
+    elffile = ELFFile(f)
+    for segment in elffile.iter_segments():
+        if isinstance(segment, InterpSegment):
+            ld = segment.get_interp_name()
+if ld is None:
+    raise Exception("could not find interpreter/ld.so path in uwsgi - failing")
 
 apppath = os.path.dirname(settings)
 sitepath = os.path.dirname(apppath)
@@ -35,8 +46,7 @@ config.write(cfgf)
 cfgf.close()
 
 args = [
-    # uwsgi from runfiles is non-chmodded, run through interpreter
+    ld,
-    '/lib64/ld-linux-x86-64.so.2',
     uwsgi,
     '--ini', cfgf.name,
 ]

third_party/py/requirements.txt

@@ -33,6 +33,7 @@ psycopg2==2.8.5
 pyasn1==0.4.5
 pycparser==2.19
 PyNaCl==1.3.0
+pyelftools==0.26
 python-dateutil==2.8.0
 pytz==2019.1
 requests==2.22.0