Show cause when ~/.netrc can't be read

doc/changelog.asciidoc

@@ -90,6 +90,8 @@ Changed
 - On Qt 5.10 or newer, dictionaries are now read from the qutebrowser data
   directory (e.g. `~/.local/share/qutebrowser`) instead of `/usr/share/qt`.
   Existing dictionaries are copied over.
+- If an error while parsing `~/.netrc` occurs, the cause of the error is now
+  logged.
 
 Fixed
 ~~~~~

qutebrowser/browser/shared.py

@@ -312,10 +312,10 @@ def netrc_authentication(url, authenticator):
             (user, _account, password) = authenticators
     except FileNotFoundError:
         log.misc.debug("No .netrc file found")
-    except OSError:
-        log.misc.exception("Unable to read the netrc file")
-    except netrc.NetrcParseError:
-        log.misc.exception("Error when parsing the netrc file")
+    except OSError as e:
+        log.misc.exception("Unable to read the netrc file: {}".format(e))
+    except netrc.NetrcParseError as e:
+        log.misc.exception("Error when parsing the netrc file: {}".format(e))
 
     if user is None:
         return False