log

        # Logger.log

(from ruby core)
---
    log(severity, message = nil, progname = nil)

---

(This method is an alias for Logger#add.)

### Args

`severity`
:   Severity.  Constants are defined in Logger namespace: `DEBUG`,
    `INFO`, `WARN`, `ERROR`, `FATAL`, or `UNKNOWN`.
`message`
:   The log message.  A String or Exception.
`progname`
:   Program name string.  Can be omitted.  Treated as a message if no
    `message` and `block` are given.
`block`
:   Can be omitted.  Called to get a message string if `message` is nil.


### Return

When the given severity is not high enough (for this particular logger),
log no message, and return `true`.

### Description

Log a message if the given severity is high enough.  This is the generic
logging method.  Users will be more inclined to use #debug, #info,
#warn, #error, and #fatal.

**Message format**: `message` can be any object, but it has to be
converted to a String in order to log it.  Generally, `inspect` is used
if the given object is not a String. A special case is an `Exception`
object, which will be printed in detail, including message, class, and
backtrace.  See #msg2str for the implementation if required.

### Bugs

*   Logfile is not locked.
*   Append open does not need to lock file.
*   If the OS supports multi I/O, records possibly may be mixed.