Don't print backtraces from inside Python.

This is done by adding a 'backtrace' boolean parameter to PrefixedOutStream.

src/mlpack/bindings/python/mlpack/cli_util.hpp

@@ -100,6 +100,14 @@ inline void EnableVerbose()
   Log::Info.ignoreInput = false;
 }
 
+/**
+ * Disable backtraces.
+ */
+inline void DisableBacktrace()
+{
+  Log::Fatal.backtrace = false;
+}
+
 } // namespace util
 } // namespace mlpack
 

src/mlpack/bindings/python/print_pyx.cpp

@@ -72,7 +72,8 @@ void PrintPYX(const ProgramDoc& programInfo,
   cout << "cimport arma_numpy" << endl;
   cout << "from cli cimport CLI" << endl;
   cout << "from cli cimport SetParam, SetParamWithInfo" << endl;
-  cout << "from cli cimport EnableVerbose" << endl;
+  cout << "from cli cimport EnableVerbose, DisableBacktrace"
+      << endl;
   cout << "from cli cimport MoveFromPtr, MoveToPtr" << endl;
   cout << "from matrix_utils import to_matrix, to_matrix_with_info" << endl;
   cout << endl;
@@ -168,6 +169,9 @@ void PrintPYX(const ProgramDoc& programInfo,
       << "returned." << endl;
   cout << "  \"\"\"" << endl;
 
+  // Disable backtraces.
+  cout << "  DisableBacktrace()" << endl;
+
   // Restore the parameters.
   cout << "  CLI.RestoreSettings(\"" << programInfo.programName << "\")";
 

src/mlpack/core/util/prefixedoutstream.hpp

@@ -54,13 +54,17 @@ class PrefixedOutStream
    * @param ignoreInput If true, the stream will not be printed.
    * @param fatal If true, a std::runtime_error exception is thrown after
    *     printing a newline.
+   * @param backtrace If true, attempt to print a backtrace (will only be
+   *     done if HAS_BFD_DL is defined).
    */
   PrefixedOutStream(std::ostream& destination,
                     const char* prefix,
                     bool ignoreInput = false,
-                    bool fatal = false) :
+                    bool fatal = false,
+                    bool backtrace = true) :
       destination(destination),
       ignoreInput(ignoreInput),
+      backtrace(backtrace),
       prefix(prefix),
       // We want the first call to operator<< to prefix the prefix so we set
       // carriageReturned to true.
@@ -113,6 +117,10 @@ class PrefixedOutStream
   //! Discards input, prints nothing if true.
   bool ignoreInput;
 
+  //! If true, on a fatal error, a backtrace will be printed if HAS_BFD_DL is
+  //! defined.
+  bool backtrace;
+
  private:
   /**
    * Conducts the base logic required in all the operator << overloads.  Mostly

src/mlpack/core/util/prefixedoutstream_impl.hpp

@@ -113,7 +113,7 @@ PrefixedOutStream::BaseLogic(const T& val)
 
     // Print a backtrace, if we can.
 #ifdef HAS_BFD_DL
-    if (fatal && !ignoreInput)
+    if (fatal && !ignoreInput && backtrace)
     {
       size_t nl;
       size_t pos = 0;