Vendor in pypy's version of py.path.local.make_numbered_dir(), which is more

resilient against random OS Errors like EACCES

testing/udir.py

 import py
-import sys
+import sys, os, atexit
+
+
+# This is copied from PyPy's vendored py lib.  The latest py lib release
+# (1.8.1) contains a bug and crashes if it sees another temporary directory
+# in which we don't have write permission (e.g. because it's owned by someone
+# else).
+def make_numbered_dir(prefix='session-', rootdir=None, keep=3,
+                      lock_timeout = 172800,   # two days
+                      min_timeout = 300):      # five minutes
+    """ return unique directory with a number greater than the current
+        maximum one.  The number is assumed to start directly after prefix.
+        if keep is true directories with a number less than (maxnum-keep)
+        will be removed.
+    """
+    if rootdir is None:
+        rootdir = py.path.local.get_temproot()
+
+    def parse_num(path):
+        """ parse the number out of a path (if it matches the prefix) """
+        bn = path.basename
+        if bn.startswith(prefix):
+            try:
+                return int(bn[len(prefix):])
+            except ValueError:
+                pass
+
+    # compute the maximum number currently in use with the
+    # prefix
+    lastmax = None
+    while True:
+        maxnum = -1
+        for path in rootdir.listdir():
+            num = parse_num(path)
+            if num is not None:
+                maxnum = max(maxnum, num)
+
+        # make the new directory
+        try:
+            udir = rootdir.mkdir(prefix + str(maxnum+1))
+        except py.error.EEXIST:
+            # race condition: another thread/process created the dir
+            # in the meantime.  Try counting again
+            if lastmax == maxnum:
+                raise
+            lastmax = maxnum
+            continue
+        break
 
@@ -3,5 +50,85 @@
 
-udir = py.path.local.make_numbered_dir(prefix = 'ffi-')
+    # put a .lock file in the new directory that will be removed at
+    # process exit
+    if lock_timeout:
+        lockfile = udir.join('.lock')
+        mypid = os.getpid()
+        if hasattr(lockfile, 'mksymlinkto'):
+            lockfile.mksymlinkto(str(mypid))
+        else:
+            lockfile.write(str(mypid))
+        def try_remove_lockfile():
+            # in a fork() situation, only the last process should
+            # remove the .lock, otherwise the other processes run the
+            # risk of seeing their temporary dir disappear.  For now
+            # we remove the .lock in the parent only (i.e. we assume
+            # that the children finish before the parent).
+            if os.getpid() != mypid:
+                return
+            try:
+                lockfile.remove()
+            except py.error.Error:
+                pass
+        atexit.register(try_remove_lockfile)
+
+    # prune old directories
+    if keep:
+        for path in rootdir.listdir():
+            num = parse_num(path)
+            if num is not None and num <= (maxnum - keep):
+                if min_timeout:
+                    # NB: doing this is needed to prevent (or reduce
+                    # a lot the chance of) the following situation:
+                    # 'keep+1' processes call make_numbered_dir() at
+                    # the same time, they create dirs, but then the
+                    # last process notices the first dir doesn't have
+                    # (yet) a .lock in it and kills it.
+                    try:
+                        t1 = path.lstat().mtime
+                        t2 = lockfile.lstat().mtime
+                        if abs(t2-t1) < min_timeout:
+                            continue   # skip directories too recent
+                    except py.error.Error:
+                        continue   # failure to get a time, better skip
+                lf = path.join('.lock')
+                try:
+                    t1 = lf.lstat().mtime
+                    t2 = lockfile.lstat().mtime
+                    if not lock_timeout or abs(t2-t1) < lock_timeout:
+                        continue   # skip directories still locked
+                except py.error.Error:
+                    pass   # assume that it means that there is no 'lf'
+                try:
+                    path.remove(rec=1)
+                except KeyboardInterrupt:
+                    raise
+                except: # this might be py.error.Error, WindowsError ...
+                    pass
+
+    # make link...
+    try:
+        username = os.environ['USER']           #linux, et al
+    except KeyError:
+        try:
+            username = os.environ['USERNAME']   #windows
+        except KeyError:
+            username = 'current'
+
+    src  = str(udir)
+    dest = src[:src.rfind('-')] + '-' + username
+    try:
+        os.unlink(dest)
+    except OSError:
+        pass
+    try:
+        os.symlink(src, dest)
+    except (OSError, AttributeError, NotImplementedError):
+        pass
+
+    return udir
+
+
+udir = make_numbered_dir(prefix = 'ffi-')
 
 
 # Windows-only workaround for some configurations: see