Change back to use pexLog.Debug directly

With the logging framework changes in pipe_base, Tasks' logs
is transitioned from pex.logging to lsst.log, and negative logging
levels are no longer used. To facilitate logging framework migration,
usage of pexLog.Debug is separated. Practically this commit reverts
part of the changes in 33520d7

python/lsst/meas/extensions/psfex/psfexPsfDeterminer.py

@@ -24,6 +24,7 @@
 
 import lsst.daf.base as dafBase
 import lsst.pex.config as pexConfig
+import lsst.pex.logging as pexLog
 import lsst.afw.geom as afwGeom
 import lsst.afw.geom.ellipses as afwEll
 import lsst.afw.display.ds9 as ds9
@@ -154,6 +155,7 @@ def determinePsf(self, exposure, psfCandidateList, metadata=None, flagKey=None):
         normalizeResiduals = lsstDebug.Info(__name__).normalizeResiduals
                                                             # Normalise residuals by object amplitude
 
+        debugLog = pexLog.Debug("meas.algorithms.psfDeterminer")
         mi = exposure.getMaskedImage()
 
         nCand = len(psfCandidateList)
@@ -175,7 +177,7 @@ def determinePsf(self, exposure, psfCandidateList, metadata=None, flagKey=None):
                 if psfCellSet:
                     psfCellSet.insertCandidate(psfCandidate)
             except Exception, e:
-                self.log.log(-2, "Skipping PSF candidate %d of %d: %s" % (i, len(psfCandidateList), e))
+                debugLog.debug(2, "Skipping PSF candidate %d of %d: %s" % (i, len(psfCandidateList), e))
                 continue
 
             source = psfCandidate.getSource()
@@ -184,7 +186,7 @@ def determinePsf(self, exposure, psfCandidateList, metadata=None, flagKey=None):
             sizes[i] = rmsSize
 
         if self.config.kernelSize >= 15:
-            self.log.log(-1, \
+            debugLog.debug(1, \
                 "WARNING: NOT scaling kernelSize by stellar quadrupole moment, but using absolute value")
             actualKernelSize = int(self.config.kernelSize)
         else:
@@ -203,7 +205,7 @@ def determinePsf(self, exposure, psfCandidateList, metadata=None, flagKey=None):
             pixKernelSize = int(actualKernelSize*self.config.samplingSize)
             if pixKernelSize % 2 == 0:
                 pixKernelSize += 1
-        self.log.log(-3, "Psfex Kernel size=%.2f, Image Kernel Size=%.2f" %
+        debugLog.debug(3, "Psfex Kernel size=%.2f, Image Kernel Size=%.2f" %
                             (actualKernelSize,pixKernelSize))
         psfCandidateList[0].setHeight(pixKernelSize)
         psfCandidateList[0].setWidth(pixKernelSize)
@@ -314,7 +316,7 @@ def determinePsf(self, exposure, psfCandidateList, metadata=None, flagKey=None):
                     for j in range(set.getNcontext()):
                         sample.setContext(j, float(contextvalp[j][i]))
                 except Exception as e:
-                    self.log.log(-2, "Exception when processing sample at (%f,%f): %s" % (xc, yc, e))
+                    debugLog.debug(2, "Exception when processing sample at (%f,%f): %s" % (xc, yc, e))
                     continue
                 else:
                     set.finiSample(sample)