Fixed Python3 bugs in lzmavalid and zlibextract plugins

src/binwalk/plugins/lzmavalid.py

 import lzma
 import binwalk.core.plugin
+import binwalk.core.compat
 from binwalk.core.common import BlockFile
 
 class LZMAPlugin(binwalk.core.plugin.Plugin):
@@ -18,14 +19,17 @@ class LZMAPlugin(binwalk.core.plugin.Plugin):
     def is_valid_lzma(self, data):
         valid = True
 
-        # The only acceptable exception is that of IOError "unknown BUF error",
-        # which indicates that the input data was truncated.
+        # The only acceptable exceptions are those indicating that the input data was truncated.
         try:
-            d = lzma.decompress(data)
+            lzma.decompress(binwalk.core.compat.str2bytes(data))
         except IOError as e:
-            if e.message != "unknown BUF error":
+            # The Python2 module gives this error on truncated input data.
+            if str(e) != "unknown BUF error":
                 valid = False
         except Exception as e:
+            # The Python3 module gives this error on truncated input data.
+            # The inconsistency between modules is a bit worrisome.
+            if str(e) != "Compressed data ended before the end-of-stream marker was reached":
                 valid = False
 
         return valid

src/binwalk/plugins/zlibextract.py

 import os
 import zlib
+import binwalk.core.compat
 import binwalk.core.common
 import binwalk.core.plugin
 
@@ -25,12 +26,12 @@ class ZLIBExtractPlugin(binwalk.core.plugin.Plugin):
             fpin = binwalk.core.common.BlockFile(fname)
             fpout = binwalk.core.common.BlockFile(outfile, 'w')
 
-            plaintext = zlib.decompress(fpin.read())
+            plaintext = zlib.decompress(binwalk.core.compat.str2bytes(fpin.read()))
             fpout.write(plaintext)
 
             fpin.close()
             fpout.close()
-        except Exception, e:
+        except Exception as e:
             return False
 
         return True