testing/conftest.py: Refactor lsof fd leak checking

Isolate the logic into one class to make easier to understand, more maintainable.
This may aid in later plugging in an alternative implementation, such as one
that uses psutil
(https://bitbucket.org/hpk42/pytest/pull-request/137/use-psutil-to-detect-open-files-in-tests/diff)

--HG--
branch : refactor_LsofFdLeakChecker

testing/conftest.py

@@ -4,7 +4,23 @@ import sys
 pytest_plugins = "pytester",
 
 import os, py
-pid = os.getpid()
+
+class LsofFdLeakChecker(object):
+    def get_open_files(self):
+        out = self._exec_lsof()
+        open_files = self._parse_lsof_output(out)
+        return open_files
+
+    def _exec_lsof(self):
+        pid = os.getpid()
+        return py.process.cmdexec("lsof -p %d" % pid)
+
+    def _parse_lsof_output(self, out):
+        def isopen(line):
+            return ("REG" in line or "CHR" in line) and (
+                "deleted" not in line and 'mem' not in line and "txt" not in line)
+        return [x for x in out.split("\n") if isopen(x)]
+
 
 def pytest_addoption(parser):
     parser.addoption('--lsof',
@@ -15,11 +31,12 @@ def pytest_configure(config):
     config._basedir = py.path.local()
     if config.getvalue("lsof"):
         try:
-            out = py.process.cmdexec("lsof -p %d" % pid)
+            config._fd_leak_checker = LsofFdLeakChecker()
+            config._openfiles = config._fd_leak_checker.get_open_files()
         except py.process.cmdexec.Error:
             pass
         else:
-            config._numfiles = len(getopenfiles(out))
+            config._numfiles = len(config._openfiles)
 
 #def pytest_report_header():
 #    return "pid: %s" % os.getpid()
@@ -31,8 +48,7 @@ def getopenfiles(out):
     return [x for x in out.split("\n") if isopen(x)]
 
 def check_open_files(config):
-    out2 = py.process.cmdexec("lsof -p %d" % pid)
-    lines2 = getopenfiles(out2)
+    lines2 = config._fd_leak_checker.get_open_files()
     if len(lines2) > config._numfiles + 3:
         error = []
         error.append("***** %s FD leackage detected" %