Remove usage of CHECK_NOTNULL

We want to switch to absl logging instead of glog.  gtest and ceres are
going there, and we already have absl as a dependency.  ABSL doesn't
have CHECK_NOTNULL, and we can move things over in an easier to review
fashion.

Change-Id: Ifd9a11ec34a2357cec43f88dba015db9c28ed2cf
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/aos/analysis/py_log_reader.cc b/aos/analysis/py_log_reader.cc
index 340140c..c190acb 100644
--- a/aos/analysis/py_log_reader.cc
+++ b/aos/analysis/py_log_reader.cc
@@ -111,7 +111,8 @@
     return -1;
   }
 
-  LogReaderTools *tools = CHECK_NOTNULL(self->tools);
+  LogReaderTools *tools = self->tools;
+  CHECK(tools != nullptr);
   tools->reader = std::make_unique<aos::logger::LogReader>(log_file_name);
   tools->reader->Register();
 
@@ -140,7 +141,8 @@
     return nullptr;
   }
 
-  LogReaderTools *tools = CHECK_NOTNULL(self->tools);
+  LogReaderTools *tools = self->tools;
+  CHECK(tools != nullptr);
 
   if (!tools->processed) {
     PyErr_SetString(PyExc_RuntimeError,
@@ -188,7 +190,8 @@
     return nullptr;
   }
 
-  LogReaderTools *tools = CHECK_NOTNULL(self->tools);
+  LogReaderTools *tools = self->tools;
+  CHECK(tools != nullptr);
 
   if (tools->processed) {
     PyErr_SetString(PyExc_RuntimeError,
@@ -217,7 +220,8 @@
 
 static PyObject *LogReader_process(LogReaderType *self,
                                    PyObject *Py_UNUSED(ignored)) {
-  LogReaderTools *tools = CHECK_NOTNULL(self->tools);
+  LogReaderTools *tools = self->tools;
+  CHECK(tools != nullptr);
 
   if (tools->processed) {
     PyErr_SetString(PyExc_RuntimeError, "process() may only be called once.");
@@ -233,7 +237,8 @@
 
 static PyObject *LogReader_configuration(LogReaderType *self,
                                          PyObject *Py_UNUSED(ignored)) {
-  LogReaderTools *tools = CHECK_NOTNULL(self->tools);
+  LogReaderTools *tools = self->tools;
+  CHECK(tools != nullptr);
 
   // I have no clue if the Configuration that we get from the log reader is in a
   // contiguous chunk of memory, and I'm too lazy to either figure it out or