Make module detection more robust and use it when possible.

doc/changelog.txt

@@ -1,5 +1,9 @@
 6.8 "" (released xx.xx.2011)
 
+Fixes:
+- checking: make module detection more robust
+
+
 Changes:
 - gui: Print detected module information in about dialog.
 - gui: Close application on Ctrl-C.

linkcheck/checker/urlbase.py

@@ -754,12 +754,11 @@ class UrlBase (object):
     def check_html (self):
         """Check HTML syntax of this page (which is supposed to be HTML)
         with the local HTML tidy module."""
-        try:
-            import tidy
-        except ImportError:
+        if not fileutil.has_module("tidy"):
             log.warn(LOG_CHECK, _("warning: tidy module is not available; " \
                  "download from http://utidylib.berlios.de/"))
             return
+        import tidy
         options = dict(output_html=0, show_warnings=1, quiet=True,
             input_encoding='utf8', output_encoding='utf8', tidy_mark=0)
         try:

linkcheck/configuration/__init__.py

@@ -339,9 +339,7 @@ class Configuration (dict):
 
     def sanitize_checkhtml (self):
         """Ensure HTML tidy is installed for checking HTML."""
-        try:
-            import tidy
-        except ImportError:
+        if not fileutil.has_module("tidy"):
             log.warn(LOG_CHECK,
                 _("warning: tidy module is not available; " \
                  "download from http://utidylib.berlios.de/"))
@@ -349,9 +347,7 @@ class Configuration (dict):
 
     def sanitize_checkcss (self):
         """Ensure cssutils is installed for checking CSS."""
-        try:
-            import cssutils
-        except ImportError:
+        if not fileutil.has_module("cssutils"):
             log.warn(LOG_CHECK,
                 _("warning: cssutils module is not available; " \
                  "download from http://cthedot.de/cssutils/"))

linkcheck/fileutil.py

@@ -65,7 +65,8 @@ def has_module (name):
     try:
         exec "import %s" % name
         return True
-    except ImportError:
+    except (OSError, ImportError):
+        # some modules (for example HTMLtidy) raise OSError
         return False