Remove no longer needed r/w lock interface base class

This interface/class was put in place when this code was being
more actively developed to ensure that both the dummy and the
actual class had the same methods, since these two classes
have apis that are now stable we no longer need to have a base
class to enforce the implemented api that itself provides no
added functionality.

Change-Id: Ida4f86b308941ff708db5395a1d266c0c4b75815

taskflow/utils/lock_utils.py

@@ -19,7 +19,6 @@
 # pulls in oslo.cfg) and is reduced to only what taskflow currently wants to
 # use from that code.
 
-import abc
 import collections
 import contextlib
 import errno
@@ -91,47 +90,7 @@ def locked(*args, **kwargs):
             return decorator
 
 
-@six.add_metaclass(abc.ABCMeta)
-class _ReaderWriterLockBase(object):
-    """Base class for reader/writer lock implementations."""
-
-    @abc.abstractproperty
-    def has_pending_writers(self):
-        """Returns if there are writers waiting to become the *one* writer."""
-
-    @abc.abstractmethod
-    def is_writer(self, check_pending=True):
-        """Returns if the caller is the active writer or a pending writer."""
-
-    @abc.abstractproperty
-    def owner(self):
-        """Returns whether the lock is locked by a writer or reader."""
-
-    @abc.abstractmethod
-    def is_reader(self):
-        """Returns if the caller is one of the readers."""
-
-    @abc.abstractmethod
-    def read_lock(self):
-        """Context manager that grants a read lock.
-
-        Will wait until no active or pending writers.
-
-        Raises a RuntimeError if an active or pending writer tries to acquire
-        a read lock.
-        """
-
-    @abc.abstractmethod
-    def write_lock(self):
-        """Context manager that grants a write lock.
-
-        Will wait until no active readers. Blocks readers after acquiring.
-
-        Raises a RuntimeError if an active reader attempts to acquire a lock.
-        """
-
-
-class ReaderWriterLock(_ReaderWriterLockBase):
+class ReaderWriterLock(object):
     """A reader/writer lock.
 
     This lock allows for simultaneous readers to exist but only one writer
@@ -154,6 +113,7 @@ class ReaderWriterLock(_ReaderWriterLockBase):
 
     @property
     def has_pending_writers(self):
+        """Returns if there are writers waiting to become the *one* writer."""
         self._cond.acquire()
         try:
             return bool(self._pending_writers)
@@ -161,6 +121,7 @@ class ReaderWriterLock(_ReaderWriterLockBase):
             self._cond.release()
 
     def is_writer(self, check_pending=True):
+        """Returns if the caller is the active writer or a pending writer."""
         self._cond.acquire()
         try:
             me = tu.get_ident()
@@ -175,6 +136,7 @@ class ReaderWriterLock(_ReaderWriterLockBase):
 
     @property
     def owner(self):
+        """Returns whether the lock is locked by a writer or reader."""
         self._cond.acquire()
         try:
             if self._writer is not None:
@@ -186,6 +148,7 @@ class ReaderWriterLock(_ReaderWriterLockBase):
             self._cond.release()
 
     def is_reader(self):
+        """Returns if the caller is one of the readers."""
         self._cond.acquire()
         try:
             return tu.get_ident() in self._readers
@@ -194,6 +157,13 @@ class ReaderWriterLock(_ReaderWriterLockBase):
 
     @contextlib.contextmanager
     def read_lock(self):
+        """Context manager that grants a read lock.
+
+        Will wait until no active or pending writers.
+
+        Raises a RuntimeError if an active or pending writer tries to acquire
+        a read lock.
+        """
         me = tu.get_ident()
         if self.is_writer():
             raise RuntimeError("Writer %s can not acquire a read lock"
@@ -226,6 +196,12 @@ class ReaderWriterLock(_ReaderWriterLockBase):
 
     @contextlib.contextmanager
     def write_lock(self):
+        """Context manager that grants a write lock.
+
+        Will wait until no active readers. Blocks readers after acquiring.
+
+        Raises a RuntimeError if an active reader attempts to acquire a lock.
+        """
         me = tu.get_ident()
         if self.is_reader():
             raise RuntimeError("Reader %s to writer privilege"
@@ -257,7 +233,7 @@ class ReaderWriterLock(_ReaderWriterLockBase):
                     self._cond.release()
 
 
-class DummyReaderWriterLock(_ReaderWriterLockBase):
+class DummyReaderWriterLock(object):
     """A dummy reader/writer lock.
 
     This dummy lock doesn't lock anything but provides the same functions as a