avocado.utils.archive: Warn of bad members inside archives

When performing tests with the latest LTP tarball, I found
a bad return from Tarfile().extract_file(), that could be
either a badly formed tarball or a Tarfile() bug. Either
way, the archive module was equipped to deal with such a
situation, not failing the test altogether.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

avocado/utils/archive.py

@@ -26,11 +26,14 @@
 """
 Library used to transparently uncompress compressed files.
 """
+import logging
 import os
 import shutil
 import tarfile
 import zipfile
 
+log = logging.getLogger('avocado.test')
+
 
 class ArchiveException(Exception):
 
@@ -172,14 +175,19 @@ class TarArchive(BaseArchive):
                 except (KeyError, AttributeError) as exc:
                     # Some corrupt tar files seem to produce this
                     # (specifically bad symlinks)
-                    print("In the tar file %s the member %s is invalid: %s" %
-                          (name, member.name, exc))
+                    log.error("In the tar file %s the member %s is "
+                              "invalid: %s" % (name, member.name, exc))
                 else:
                     dirname = os.path.dirname(filename)
                     if dirname and not os.path.exists(dirname):
                         os.makedirs(dirname)
                     with open(filename, 'wb') as outfile:
+                        if extracted is not None:
                             shutil.copyfileobj(extracted, outfile)
+                        else:
+                            log.error("Member correspondent to file %s does "
+                                      "not seem to be a regular file or a link",
+                                      filename)
                 finally:
                     if extracted:
                         extracted.close()