Revert "depot_tools: Ensure Python is bootstrapped before reading python3_bin_reldir.txt"

This reverts commit bf26b167a8.

Reason for revert: spec revert for https://bugs.chromium.org/p/chromium/issues/detail?id=1025659

Original change's description:
> depot_tools: Ensure Python is bootstrapped before reading python3_bin_reldir.txt
> 
> Bug: 1017812
> Change-Id: I7013e5445ff5917fab813a54fed416d9770d2684
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1913269
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>

TBR=dpranke@chromium.org,ehmaldonado@chromium.org,apolito@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1017812
Change-Id: I8e10894a2e835c20ece7d555c21f6ce1f76528a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1922949
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>

vpython

@@ -34,20 +34,13 @@ then
 fi
 
 
-base_dir=$(dirname "$0")
+MYPATH=$(dirname "${BASH_SOURCE[0]}")
 
-source "$base_dir/cipd_bin_setup.sh"
+source "$MYPATH/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null
 
-# If Python bootstrapping is not disabled, make sure Python has been
-# bootstrapped and add it to the front of PATH.
-if [[ $MINGW != 0 && $DEPOT_TOOLS_BOOTSTRAP_PYTHON3 != 0 ]]; then
-  if [[ ! -e $base_dir/python_bin_reldir.txt ]]; then
-    source "$base_dir/bootstrap_python3"
-    bootstrap_python3
-  fi
-  PYTHON_BIN_RELDIR="$base_dir/$(cat $base_dir/python_bin_reldir.txt | xargs echo)"
+base_dir=$(dirname "$0")
+PYTHON_BIN_RELDIR="$(cat $base_dir/python_bin_reldir.txt | xargs echo)"
 PATH="$PYTHON_BIN_RELDIR":"$PYTHON_BIN_RELDIR/Scripts":"$PATH"
-fi
 
-exec "$base_dir/.cipd_bin/vpython" "$@"
+exec "$MYPATH/.cipd_bin/vpython" "$@"

vpython3

@@ -34,20 +34,13 @@ then
 fi
 
 
-base_dir=$(dirname "$0")
+MYPATH=$(dirname "${BASH_SOURCE[0]}")
 
-source "$base_dir/cipd_bin_setup.sh"
+source "$MYPATH/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null
 
-# If Python bootstrapping is not disabled, make sure Python has been
-# bootstrapped and add it to the front of PATH.
-if [[ $MINGW != 0 && $DEPOT_TOOLS_BOOTSTRAP_PYTHON3 != 0 ]]; then
-  if [[ ! -e $base_dir/python3_bin_reldir.txt ]]; then
-    source "$base_dir/bootstrap_python3"
-    bootstrap_python3
-  fi
-  PYTHON3_BIN_RELDIR="$base_dir/$(cat $base_dir/python3_bin_reldir.txt | xargs echo)"
+base_dir=$(dirname "$0")
+PYTHON3_BIN_RELDIR="$(cat $base_dir/python3_bin_reldir.txt | xargs echo)"
 PATH="$PYTHON3_BIN_RELDIR":"$PYTHON3_BIN_RELDIR/Scripts":"$PATH"
-fi
 
-exec "$base_dir/.cipd_bin/vpython3" "$@"
+exec "$MYPATH/.cipd_bin/vpython3" "$@"